revert changes in ReactCodegen template (#52257)

Summary:
After switching to the new backwards compatible cocoapods structure with prebuilts, we no longer need any change in the ReactCodegen template.

This commit fixes this.

## Changelog:

[IOS] [FIXED] - revert changes in ReactCodegen template

Pull Request resolved: https://github.com/facebook/react-native/pull/52257

Test Plan: Build RN-tester with prebuilt

Reviewed By: cortinico

Differential Revision: D77303429

Pulled By: cipolleschi

fbshipit-source-id: d251d7d67b1c902082891ba705db5158c558e842