Simplify the code of `animationRepeatCount`, since there are no override logic

SDWebImage/SDAnimatedImageView.m

@@ -66,7 +66,7 @@ static NSUInteger SDDeviceFreeMemory() {
 
 @implementation SDAnimatedImageView
 #if SD_UIKIT
-@dynamic animationRepeatCount;
+@dynamic animationRepeatCount; // we re-use this property from `UIImageView` super class on iOS.
 #endif
 
 #pragma mark - Initializers
@@ -238,15 +238,6 @@ static NSUInteger SDDeviceFreeMemory() {
     }
 }
 
-- (void)setAnimationRepeatCount:(NSInteger)animationRepeatCount
-{
-#if SD_MAC
-    _animationRepeatCount = animationRepeatCount;
-#else
-    [super setAnimationRepeatCount:animationRepeatCount];
-#endif
-}
-
 #if SD_UIKIT
 - (void)setRunLoopMode:(NSString *)runLoopMode
 {