Fix TestAccDataSourceNotFound test

[adambarreiro]

Fixes failures:

FAIL: TestAccDataSourceNotFound/vcfa_certificate (0.60s) ---
FAIL: TestAccDataSourceNotFound/vcfa_org_local_user (0.18s) ---
FAIL: TestAccDataSourceNotFound/vcfa_org_regional_networking_vpc_qos (0.19s)

Also bumps SDK to an alpha tag, which was not done in #26. To avoid these mistakes, I added also a GitHub action that checks that no replace is in go.mod when a PR approval event is triggered.

I think changelog entry is not needed here as nothing new is introduced, but let me know otherwise.

[Didainius]

Thank you for fixes. Maybe a note in changelog for catching the replace directive