code_style: remove unused code

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Views/ColorPicker.cs

@@ -83,11 +83,6 @@ public uint Value
             }
         };
 
-        static ColorPicker()
-        {
-            ValueProperty.Changed.AddClassHandler<ColorPicker>((c, _) => c.UpdateColors());
-        }
-
         public override void Render(DrawingContext context)
         {
             base.Render(context);

src/Views/RevisionFileTreeView.axaml.cs

@@ -54,10 +54,12 @@ public bool IsExpanded
             set => SetValue(IsExpandedProperty, value);
         }
 
-        static RevisionTreeNodeIcon()
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
-            NodeProperty.Changed.AddClassHandler<RevisionTreeNodeIcon>((icon, _) => icon.UpdateContent());
-            IsExpandedProperty.Changed.AddClassHandler<RevisionTreeNodeIcon>((icon, _) => icon.UpdateContent());
+            base.OnPropertyChanged(change);
+
+            if (change.Property == NodeProperty || change.Property == IsExpandedProperty)
+                UpdateContent();
         }
 
         private void UpdateContent()