Remove `build-setup-requires-pex` options scope. (#9732)
Remove `build-setup-requires-pex` options scope. (#9732)

This has been moved to the `setup-py-runner` options scope.
pantsbuild/pants,pantsbuild/pants,pantsbuild/pants,pantsbuild/pants,jsirois/pants,benjyw/pants,jsirois/pants,benjyw/pants,jsirois/pants,benjyw/pants,benjyw/pants,pantsbuild/pants,benjyw/pants,benjyw/pants,pantsbuild/pants,pantsbuild/pants,benjyw/pants