Update the comment about scale factor for coders

SDWebImage/SDImageCoder.h

@@ -51,7 +51,6 @@ FOUNDATION_EXPORT SDImageCoderOption _Nonnull const SDImageCoderWebImageContext;
 /**
  This is the image coder protocol to provide custom image decoding/encoding.
  These methods are all required to implement.
- You do not need to specify image scale during decoding because we may scale image later.
  @note Pay attention that these methods are not called from main queue.
  */
 @protocol SDImageCoder <NSObject>
@@ -71,7 +70,7 @@ FOUNDATION_EXPORT SDImageCoderOption _Nonnull const SDImageCoderWebImageContext;
  @note This protocol may supports decode animated image frames. You can use `+[SDImageCoderHelper animatedImageWithFrames:]` to produce an animated image with frames.
 
  @param data The image data to be decoded
- @param options A dictionary containing any decoding options. Pass @{SDImageCoderDecodeFirstFrameOnly: @(YES)} to decode the first frame only.
+ @param options A dictionary containing any decoding options. Pass @{SDImageCoderDecodeScaleFactor: @(1.0)} to specify scale factor for image. Pass @{SDImageCoderDecodeFirstFrameOnly: @(YES)} to decode the first frame only.
  @return The decoded image from data
  */
 - (nullable UIImage *)decodedImageWithData:(nullable NSData *)data

SDWebImage/SDWebImageManager.m

@@ -108,10 +108,6 @@ static id<SDImageLoader> _defaultImageLoader;
     }
 }
 
-- (nullable UIImage *)scaledImageForKey:(nullable NSString *)key image:(nullable UIImage *)image {
-    return SDScaledImageForKey(key, image);
-}
-
 - (SDWebImageCombinedOperation *)loadImageWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDImageLoaderProgressBlock)progressBlock completed:(SDInternalCompletionBlock)completedBlock {
     return [self loadImageWithURL:url options:options context:nil progress:progressBlock completed:completedBlock];
 }