[v1.14 test] Fix maintenance job launched immediately after prune error

[qiuming-best]

Thank you for contributing to Velero!

Please add a summary of your change

Does your change fix a particular issue?

Fixes #(issue) https://github.com/vmware-tanzu/velero/issues/7744

Only enqueue Spec updates, not the Status updates

Please indicate you've done the following:

• [ ] Accepted the DCO. Commits without the DCO will delay acceptance.
• [ ] Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• [ ] Updated the corresponding documentation in site/content/docs/main.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 58.66%. Comparing base (159a49f) to head (5eae542). Report is 2 commits behind head on main.

Files	Patch %	Lines
pkg/controller/backup_repository_controller.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7745 +/- ## ======================================= Coverage 58.66% 58.66% ======================================= Files 344 344 Lines 28723 28720 -3 ======================================= Hits 16849 16849 + Misses 10445 10442 -3 Partials 1429 1429 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.