Finalize BBM FixGitlabSubscriptionHistoriesHostedPlanNameUid

What does this MR do and why?

Issue: #607406 (closed)

Finalizes the FixGitlabSubscriptionHistoriesHostedPlanNameUid batched background migration, queued in 19.3 by !246818 (merged). This unblocks the uid reads in #596995 (closed) / !242975 (merged).

The migration is finished on production:

/chatops gitlab run batched_background_migrations status 3001201 --database main

ID: 3001201
Job class: FixGitlabSubscriptionHistoriesHostedPlanNameUid
Table: gitlab_subscription_histories
Status: finished
Progress: 100%
Created at: 2026-08-13T02:14:44Z

The BBM was queued in 19.3. This MR passes skip_early_finalization_validation: true instead. The early-finalization guard protects self-managed upgrades from running a large backfill inline; gitlab_subscription_histories only holds GitLab.com subscription data, so an inline finalize on a self-managed 19.2 → 19.4 hop touches few or no rows.

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