Requeue migration to backfill sharding key for deploy_tokens

What does this MR do and why?

Requeue migration to backfill sharding key for deploy_tokens

After the original migration ran it was discovered that records without sharding keys were still being created by the application in some cases. This has since been fixed in !162669 (merged), and the backfill can now be run again to fix records that were created in the meantime.

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Related to #462932 (closed)