Remove explicitly add png file extension when load local image (#23864)

Summary:
We need to remove adding png file extension when path has not extension. Two reasons:
1. `imageWithContentsOfFile` or other `UIKit` methods can load png image correctly, even if path has not `png` file extension.
2. Sometimes, people may have file that actually not have file extension, it's the designated behavior for user. Like #23844 .

CC. sahrens cpojer .

[iOS] [Fixed] - Remove explicitly add png file extension when load local image
Pull Request resolved: https://github.com/facebook/react-native/pull/23864

Reviewed By: shergin

Differential Revision: D14425373

Pulled By: hramos

fbshipit-source-id: 3cc06c9a3d68cadf652c1de742f3cce26258c874

Libraries/Image/RCTImageLoader.m

@@ -380,11 +380,6 @@ static UIImage *RCTResizeImageIfNeeded(UIImage *image,
     [NSURLProtocol setProperty:@"RCTImageLoader"
                         forKey:@"trackingName"
                      inRequest:mutableRequest];
-
-    // Add missing png extension
-    if (request.URL.fileURL && request.URL.pathExtension.length == 0) {
-      mutableRequest.URL = [request.URL URLByAppendingPathExtension:@"png"];
-    }
     if (_redirectDelegate != nil) {
       mutableRequest.URL = [_redirectDelegate redirectAssetsURL:mutableRequest.URL];
     }

React/Base/RCTUtils.m

@@ -711,9 +711,6 @@ UIImage *__nullable RCTImageFromLocalAssetURL(NSURL *imageURL)
   if (!image) {
     // Attempt to load from the file system
     NSString *filePath = [NSString stringWithUTF8String:[imageURL fileSystemRepresentation]];
-    if (filePath.pathExtension.length == 0) {
-      filePath = [filePath stringByAppendingPathExtension:@"png"];
-    }
     image = [UIImage imageWithContentsOfFile:filePath];
   }