remove unnecessary code

YYWebImage/Categories/UIImage+YYWebImage.m

@@ -221,7 +221,7 @@ static NSTimeInterval _yy_CGImageSourceGetGIFFrameDelayAtIndex(CGImageSourceRef
             CFRelease(imageRef);
             return nil;
         }
-        UIImage *image = image = [UIImage imageWithCGImage:decoded scale:scale orientation:UIImageOrientationUp];
+        UIImage *image = [UIImage imageWithCGImage:decoded scale:scale orientation:UIImageOrientationUp];
         CGImageRelease(imageRef);
         CGImageRelease(decoded);
         if (!image) {