Remove the unused extra copy for `SDAnimatedImage` data initializer

SDWebImage/Core/SDAnimatedImage.m

@@ -124,7 +124,6 @@ static CGFloat SDImageScaleFromPath(NSString *string) {
     if (!data || data.length == 0) {
         return nil;
     }
-    data = [data copy]; // avoid mutable data
     id<SDAnimatedImageCoder> animatedCoder = nil;
     for (id<SDImageCoder>coder in [SDImageCodersManager sharedManager].coders.reverseObjectEnumerator) {
         if ([coder conformsToProtocol:@protocol(SDAnimatedImageCoder)]) {