macos: two tests are failing under GHA

[ssbarnea]

When running the testing under GHA, two tests are failing:

test_gpg_verify_manifest_scenario[valid checksum file and signature]

Error: 1mE       AssertionError: assert 'GPG signature verification succeeded' in '[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n'
[120](https://github.com/ansible/ansible-sign/actions/runs/8470365093/job/23207910758?pr=50#step:7:121)
Error:     +  where '[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n' = CaptureResult(out='[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n', err='').out

test_gpg_verify_manifest_scenario[valid signature but broken checksum file]
Error: 1mE       AssertionError: assert 'Invalid line encountered in checksum manifest' in '[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n'
[171](https://github.com/ansible/ansible-sign/actions/runs/8470365093/job/23207910758?pr=50#step:7:172)
Error:     +  where '[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n' = CaptureResult(out='[ERROR] GPG signature verification failed.\n[NOTE ] Re-run with the global --debug flag for more information.\n', err='').out

I was not able to reproduce the problem under my own machine, so I raised the bug for future tracking. We will temporary allow these two tests to fail in order to allow the CI to test other changes.