Use standard commit for merge commits on the train ref

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/129820



Merged-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Approved-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Approved-by: Albert Salim <asalim@gitlab.com>
Reviewed-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Reviewed-by: Hordur Freyr Yngvason <hfyngvason@gitlab.com>
Reviewed-by: Albert Salim <asalim@gitlab.com>
Co-authored-by: Allison Browne <abrowne@gitlab.com>