Schedule artifact expiry date backfill

What does this MR do?

Fixes the error introduced with !47723 (merged) and reschedules correctly the BackfillArtifactExpiryDate background migration jobs

Related #298813 (closed)

Blocked by and should follow the successful merge of !51821 (merged)

Does this MR meet the acceptance criteria?

Conformity

• N/A Changelog entry
• N/A Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• N/A Separation of EE specific content