Cleanup for converted ci_stages.pipeline_id conversion

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/137379



Merged-by: Marius Bobin <mbobin@gitlab.com>
Approved-by: Marius Bobin <mbobin@gitlab.com>
Reviewed-by: Ethan Urie <eurie@gitlab.com>
Reviewed-by: Tianwen Chen <tchen@gitlab.com>
Co-authored-by: Tianwen Chen <tchen@gitlab.com>