Remove Old Arch build jobs (#44729)

Summary:
Based on https://github.com/facebook/react-native/issues/44723.
This PR removes some Old Arch build only jobs on iOS.
Some of the recent changes where unifying the build process across archs, so we don't have to build Old and New Arch

## Changelog:
[Internal] - Remove OldArch jobs when they are not required

Pull Request resolved: https://github.com/facebook/react-native/pull/44729

Test Plan: CCI is green

Reviewed By: cortinico

Differential Revision: D57975238

Pulled By: cipolleschi

fbshipit-source-id: ffd0ff0534f25019d501aa3862baee1442088784