refactor: Remove unnecessary clearing of failed media IDs

This was originally added in an attempt to clear an unexpected "failed
media upload" notification displayed after closing the editor. However,
it did not resolve that issue, it must originate from some other
location. Additionally, it would appears successful media uploads
already manage removing media IDs from the `mFailedMediaIds` collection.

libs/editor/src/main/java/org/wordpress/android/editor/gutenberg/GutenbergEditorFragment.java

@@ -1585,7 +1585,6 @@ public void onConnectionStatusChange(boolean isConnected) {
         getGutenbergContainerFragment().onConnectionStatusChange(isConnected);
         if (BuildConfig.DEBUG && hasFailedMediaUploads()) {
             mEditorFragmentListener.onMediaRetryAll(mFailedMediaIds);
-            mFailedMediaIds.clear();
         }
     }
 }