Cleanup delete orphaned deployments background migration

This commit cleans up the background migration
we introduced in the previous milestone for orphaned deployments.

Changelog: other

db/post_migrate/20211011152701_cleanup_delete_orphaned_deployments_background_migration.rb

+# frozen_string_literal: true
+
+class CleanupDeleteOrphanedDeploymentsBackgroundMigration < Gitlab::Database::Migration[1.0]
+  MIGRATION = 'DeleteOrphanedDeployments'
+
+  disable_ddl_transaction!
+
+  def up
+    finalize_background_migration(MIGRATION)
+  end
+
+  def down
+    # no-op
+  end
+end

db/schema_migrations/20211011152701

+5701681a1006584149c88da520f780b186ca32ba1facb8b952252c6d426b6c0d
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