Fix image source size props in getDiffProps (facebook#51222)

Summary:
Pull Request resolved: facebook#51222

The size parameters are flattened in the source object in the Android image component. This diff converts the `size` object to `width` and `height` props directly set on the source object, fixing image source setting more than one image source.

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D74477884

fbshipit-source-id: f6064b4222d5eeafd5d74f9a2044babedd1e291b

Author: Nick Lefever

packages/react-native/ReactCommon/react/renderer/components/image/ImageProps.cpp

@@ -194,10 +194,8 @@ static folly::dynamic convertImageSource(const ImageSource& imageSource) {
   imageSourceResult["bundle"] = imageSource.bundle;
   imageSourceResult["scale"] = imageSource.scale;
 
-  folly::dynamic size = folly::dynamic::object();
-  size["width"] = imageSource.size.width;
-  size["height"] = imageSource.size.height;
-  imageSourceResult["size"] = size;
+  imageSourceResult["width"] = imageSource.size.width;
+  imageSourceResult["height"] = imageSource.size.height;
 
   imageSourceResult["body"] = imageSource.body;
   imageSourceResult["method"] = imageSource.method;