Feat/ios m1 improvements (#32296)

Summary:
* Remove left over from https://github.com/facebook/react-native/commit/a1c445a39c580037ada4a5d194a0d2daef15a25a#commitcomment-57240925
* Add a warning if running with Rosetta2 as per https://github.com/facebook/react-native/pull/32284#issuecomment-929680784

## Changelog

[iOS] [Fixed] - Removed __apply_Xcode_12_5_M1_post_install_workaround
[iOS] [Changed] - Warn if Rosetta2 is being used (x86_64 on arm64)

Pull Request resolved: https://github.com/facebook/react-native/pull/32296

Test Plan: Build on macOS Apple devices without any warnings during `pod install`

Reviewed By: RSNara

Differential Revision: D31291567

Pulled By: fkgozali

fbshipit-source-id: 65e54507dedcdba39c1b441aad85e940eedc8b52