Remove unused FallbackJSBundleLoader (#49005)

Summary:
Pull Request resolved: #49005

This is essentially dead code. Not used at all but publicly exposed.
I found no meaningful usages in OSS so this is safe to remove:
https://github.com/search?type=code&q=NOT+is%3Afork+NOT+org%3Afacebook+NOT+repo%3Areact-native-tvos%2Freact-native-tvos+NOT+repo%3Anuagoz%2Freact-native+NOT+repo%3A2lambda123%2Freact-native+NOT+repo%3Apvinis%2Freact-native---investigation+NOT+repo%3Abeanchips%2Ffacebookreactnative+NOT+repo%3AfabOnReact%2Freact-native-notes+NOT+user%3Ahuntie+com.facebook.react.bridge.FallbackJSBundleLoader

Changelog:
[Internal] [Changed] -

Reviewed By: mdvacca

Differential Revision: D68773273

fbshipit-source-id: 96a028cb0caf95ee899db1488dbf5ae82cc567f9

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -768,11 +768,6 @@ public class com/facebook/react/bridge/DynamicFromObject : com/facebook/react/br
 	public fun recycle ()V
 }
 
-public final class com/facebook/react/bridge/FallbackJSBundleLoader : com/facebook/react/bridge/JSBundleLoader {
-	public fun <init> (Ljava/util/List;)V
-	public fun loadScript (Lcom/facebook/react/bridge/JSBundleLoaderDelegate;)Ljava/lang/String;
-}
-
 public abstract class com/facebook/react/bridge/GuardedAsyncTask : android/os/AsyncTask {
 	protected fun <init> (Lcom/facebook/react/bridge/JSExceptionHandler;)V
 	protected fun <init> (Lcom/facebook/react/bridge/ReactContext;)V