Finalize BackfillShardingKeyIdOnCiRunners background migration

What does this MR do and why?

This MR finalizes the BackfillShardingKeyIdOnCiRunners background migration which was merged in the required stop %17.5 milestone.

This migration was finished at 2024-10-05 22:35:53 UTC, you can confirm the status using our batched background migration chatops commands. To confirm it is finished you can run:

/chatops run batched_background_migrations status 1000339 --database ci

The last time this background migration was triggered was in db/post_migrate/20240923132401_queue_backfill_sharding_key_id_on_ci_runners.rb

You can read more about the process for finalizing batched background migrations in https://docs.gitlab.com/ee/development/database/batched_background_migrations.html.

As part of our process we want to ensure all batched background migrations have had at least one required stop to process the migration. Therefore we can finalize any batched background migration that was added before the last required stop.

This change was generated by gitlab-housekeeper using the Keeps::OverdueFinalizeBackgroundMigration keep.

To provide feedback on your experience with gitlab-housekeeper please create an issue with the label GitLab Housekeeper and consider pinging the author of this keep.

Changelog: other

Part of #493384 (closed)

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