Finalize DeleteOrphanedBuildRecords migration

What does this MR do and why?

Finalize DeleteOrphanedBuildRecords migration

Changelog: other

References

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• BBM: !165727 (merged) added in 17.4
• https://docs.gitlab.com/ee/development/database/batched_background_migrations.html#finalize-a-batched-background-migration
• 17.5 was a required stop: https://docs.gitlab.com/ee/update/upgrade_paths.html

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Related to #498861 (closed)