Cache property changed delegate.

src/Avalonia.Animation/AnimationInstance`1.cs

@@ -37,6 +37,7 @@ namespace Avalonia.Animation
         private IDisposable _timerSub;
         private readonly IClock _baseClock;
         private IClock _clock;
+        private EventHandler<AvaloniaPropertyChangedEventArgs> _propertyChangedDelegate;
 
         public AnimationInstance(Animation animation, Animatable control, Animator<T> animator, IClock baseClock, Action OnComplete, Func<double, T, T> Interpolator)
         {
@@ -79,7 +80,7 @@ namespace Avalonia.Animation
             // Animation may have been stopped before it has finished.
             ApplyFinalFill();
 
-            _targetControl.PropertyChanged -= ControlPropertyChanged;
+            _targetControl.PropertyChanged -= _propertyChangedDelegate;
             _timerSub?.Dispose();
             _clock.PlayState = PlayState.Stop;
         }
@@ -88,7 +89,8 @@ namespace Avalonia.Animation
         {
             _clock = new Clock(_baseClock);
             _timerSub = _clock.Subscribe(Step);
-            _targetControl.PropertyChanged += ControlPropertyChanged;
+            _propertyChangedDelegate ??= ControlPropertyChanged;
+            _targetControl.PropertyChanged += _propertyChangedDelegate;
             UpdateNeutralValue();
         }