Merge branch 'document-note-about-pipeline-execution-policy-override_project_ci' into 'master'

Add document note about PEP override_project_ci

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/158608



Merged-by: Russell Dickenson <rdickenson@gitlab.com>
Approved-by: Martin Čavoj <mcavoj@gitlab.com>
Approved-by: Russell Dickenson <rdickenson@gitlab.com>
Reviewed-by: Martin Čavoj <mcavoj@gitlab.com>
Co-authored-by: Andy Soiron <asoiron@gitlab.com>