fix space used in Objective-C method (coding style)

UIKit+AFNetworking/AFAutoPurgingImageCache.m

@@ -37,7 +37,7 @@
 
 @implementation AFCachedImage
 
--(instancetype)initWithImage:(UIImage *)image identifier:(NSString *)identifier {
+- (instancetype)initWithImage:(UIImage *)image identifier:(NSString *)identifier {
     if (self = [self init]) {
         self.image = image;
         self.identifier = identifier;