Finalize MarkPackagesHelmMetadataCachesPendingDestruction migration

What does this MR do and why?

We added MarkPackagesHelmMetadataCachesPendingDestruction in %18.4 (Add BBM to mark `packages_helm_metadata_caches`... (!203393 - merged) • Sylvia Shen • 18.4), it's already finished now and included in milestone %18.4.

/chatops run batched_background_migrations status 2001055 --database main

/chatops run release check https://gitlab.com/gitlab-org/gitlab/-/merge_requests/203393 18.4

References

• Add post migration to mark caches as pending_de... (#566574 - closed) • Sylvia Shen • 18.4

Screenshots or screen recordings

N/A

How to set up and validate locally

gdk rails db:migrate

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #570502 (closed)