gtk: Make arrow icon in modelbutton dim

src/gtk/sass/_common-3.20.scss

@@ -864,6 +864,13 @@ modelbutton.flat,

                                
                                
                                
                            
                                
                                    
                                        
                                            864  
                                            }
                                        
                                        
                                            
                                            
                                            
                                            
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        
                                            865  
                                            
                                        
                                        
                                            
                                            
                                            
                                            
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        
                                            866  
                                            modelbutton.flat arrow {
                                        
                                        
                                            
                                            
                                            
                                            
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        867 +
                                          transition: color $duration $ease-out;
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        868 +
                                          color: hint($on-surface);
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        869 +
                                        
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        870 +
                                          &:disabled {
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        871 +
                                            color: disabled-hint($on-surface);
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        872 +
                                          }
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        873 +
                                        
                                        
                                        
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        
                                            874  
                                              &.left {
                                        
                                        
                                            
                                            
                                            
                                            
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        
                                            875  
                                                -gtk-icon-source: -gtk-icontheme("pan-start-symbolic");
                                        
                                        
                                            
                                            
                                            
                                            
                                        
                                    
                                
                                
                                
                            
                                
                                    
                                        
                                            876  
                                              }