change to angled include in umbrella (#54840)

Summary:
To make the later VFS overlays work, our React umbrella header needs to use angled import syntax instead of quoted".

This is so that the compiler will look up by module and not only by path.

Prev PR: #54839
Next PR: #54841

## Changelog:

[IOS] [FIXED] - changed umbrella header template to use angled import syntax

Pull Request resolved: #54840

Test Plan: Run RNTester with prebuilds

Reviewed By: cortinico

Differential Revision: D89377015

Pulled By: cipolleschi

fbshipit-source-id: b1be8223b7cad5d09a918464f7bac6edad4bd051

Author: chrfalch