Clean up the FinalizeBackfillCiRunnerMachinesPartitionedTable migration

What does this MR do and why?

This MR no-ops and cleans up the FinalizeBackfillCiRunnerMachinesPartitionedTable migration, as it references a job class that no longer exists. The job class was removed as part of #520092 (closed), but we missed this finalization migration. In the future, similar situations will be caught during MR review once we implement #534917.

Changelog: other

References

• Clean up failed BackfillCiRunnerMachinesPartiti... (#534905 - closed)
• 17.5 to 17.8 upgrade: BBM fails with insert or ... (#520092 - closed)

Backports

• [17.10 Backport] Clean up the FinalizeBackfillC... (!187370 - merged)
• [17.9 Backport] Clean up the FinalizeBackfillCi... (!187368 - merged)

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.