Fix OverdueFinalizeBackgroundMigration#database_name

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/184021



Merged-by: Omar Qunsul <oqunsul@gitlab.com>
Approved-by: Omar Qunsul <oqunsul@gitlab.com>
Approved-by: Bishwa Hang Rai <bhrai@gitlab.com>
Co-authored-by: Maxime Orefice <morefice@gitlab.com>