jobs: make expiration use intended txn priority

[rafiss]

In aed014f these operations were supposed to be changed to use
MinUserPriority. However, they weren't using the appropriate txn, so it
didn't have the intended effect.

Release note: None

[cockroach-teamcity]

This change is 

[ajwerner]

Thank you for doing it!

Reviewed 1 of 1 files at r1.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @rafiss)

[rafiss]

tftr! failures are flakes from #85944

bors r=ajwerner

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from e04fb99 to blathers/backport-release-21.2-85930: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 21.2.x failed. See errors above.

---

error creating merge commit from e04fb99 to blathers/backport-release-22.1-85930: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.1.x failed. See errors above.

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