Code review comment for ~paride/autopkgtest-cloud:pre-commit-pylint

I updated the branch to use the canonical-ubuntu-qa/backport-pre-commit PPA. We'll be able to drop once we switch the infra to Jammy. (I may even backport pre-commit to the -backports pocket at some point, given that all it takes is a straightforward no-change rebuild.)

This is ready for review again.