Delete orphaned records on ci_runner_machines_687967fa8a table on .com

After finalizing the backfill of ci_runners_e59bb2812d on .com, we need to delete records on ci_runner_machines_687967fa8a that don't exist in ci_runners_e59bb2812d. Only after that is done, can we validate the fk_rails_3f92913d27 FK constraint.