remove ReactFragmentActivity (#30331)

Summary:
Remove ReactFragmentActivity class, which was deprecated at least since 0.58.

## Changelog

[Android] [Changed] - remove ReactFragmentActivity class.

Pull Request resolved: #30331

Reviewed By: makovkastar

Differential Revision: D24914082

Pulled By: fkgozali

fbshipit-source-id: 6833b76552a1fc19680f96501d4b8e2ff03c2c39

Author: dulmandakh

ReactAndroid/src/main/java/com/facebook/react/ReactActivityDelegate.java

@@ -20,9 +20,9 @@
 import com.facebook.react.modules.core.PermissionListener;
 
 /**
- * Delegate class for {@link ReactActivity} and {@link ReactFragmentActivity}. You can subclass this
- * to provide custom implementations for e.g. {@link #getReactNativeHost()}, if your Application
- * class doesn't implement {@link ReactApplication}.
+ * Delegate class for {@link ReactActivity}. You can subclass this to provide custom implementations
+ * for e.g. {@link #getReactNativeHost()}, if your Application class doesn't implement {@link
+ * ReactApplication}.
  */
 public class ReactActivityDelegate {