Summary:
In an app using `UIScene`, `Alert` no longer pops up because the window
that gets created are not attached to a scene.
## Changelog
[iOS] [Fixed] - Fix `Alert` not showing in an app using `UIScene`
Pull Request resolved: https://github.com/facebook/react-native/pull/34562
Test Plan: Use the test plan in https://github.com/facebook/react-native/issues/29295. This should not regress that fix.
Reviewed By: cipolleschi
Differential Revision: D39276976
Pulled By: lunaleaps
fbshipit-source-id: e48e985ed4abec77d6f01a6c17292d664ed88f13
Tommy Nguyen
153aedce41