Re Reschedule Delete Orphaned Deployments BG migration

What does this MR do and why?

Re-schedule of !66813 (merged). We can't move onto finalizing BG migration due to the database guideline that doesn't allow 90-minute sync cleanup. Since we've fixed the retry bug on BG migration and there are no issues on DeleteOrphanedDeployments migration itself, we can simply re-enqueue the jobs from background_migration_jobs table.

Please see this MR for more context. This approach follows the rescheduling guideline, which is based on this suggestion.

Screenshots or screen recordings

shinya@shinya-B550-VISION-D:~/workspace/thin-gdk/services/rails/src$ tre bin/rails db:migrate:redo VERSION=20211005010101
INFO: This script is a predefined script in devkitkat.
WARNING: This version of GitLab depends on gitlab-shell 13.21.1, but you're running 13.21.0. Please update gitlab-shell.
WARNING: This installation of GitLab uses a deprecated syntax for 'config/database.yml'. The support for this syntax will be removed in 15.0. More information can be found here: https://gitlab.com/gitlab-org/gitlab/-/issues/338182
== 20211005010101 RerescheduleDeleteOrphanedDeployments: reverting ============
== 20211005010101 RerescheduleDeleteOrphanedDeployments: reverted (0.0000s) ===

== 20211005010101 RerescheduleDeleteOrphanedDeployments: migrating ============
-- Scheduled 0 DeleteOrphanedDeployments jobs with an interval of 120 seconds.

The migration is expected to take at least 0 seconds. Expect all jobs to have completed after 2021-10-05 03:52:55 UTC."
== 20211005010101 RerescheduleDeleteOrphanedDeployments: migrated (0.0176s) ===

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