Requeue BackfillPCiPipelineVariablesProjectId

Ref: #463244 (closed)

What does this MR do and why?

This MR requeues our migration to populate project_id for p_ci_pipeline_variables as the migration has been stuck since 2024-09-26.

The idea here to reschedule this migration only for gitlab.com.

gitlabhq_dblab=#  SELECT migration.id, migration.job_class_name, transition_logs.exception_class, transition_logs.exception_message
 FROM batched_background_migrations as migration
 INNER JOIN batched_background_migration_jobs as jobs
 ON jobs.batched_background_migration_id = migration.id
 INNER JOIN batched_background_migration_job_transition_logs as transition_logs
 ON transition_logs.batched_background_migration_job_id = jobs.id
 WHERE transition_logs.next_status = '2' AND migration.job_class_name = 'BackfillPCiPipelineVariablesProjectId' limit 1;
   id    |            job_class_name             |  exception_class  | exception_message
---------+---------------------------------------+-------------------+-------------------
 1000333 | BackfillPCiPipelineVariablesProjectId | Sidekiq::Shutdown | Sidekiq::Shutdown


gitlabhq_dblab=# select id, batch_size, created_at, updated_at from batched_background_migration_jobs where batched_background_migration_id IN (1000333) order by updated_at desc limit 1;
   id    | batch_size |          created_at           |          updated_at
---------+------------+-------------------------------+-------------------------------
 1203877 |     228471 | 2024-09-26 10:27:07.201853+00 | 2024-09-26 10:29:05.097269+00
(10 rows)

https://docs.gitlab.com/ee/development/database/batched_background_migrations.html#re-queue-batched-background-migrations