Update docs for handling flaky CI runs

> At some point we should probably write something about the flakey state of CI, and that maintainers may need to re-run jobs. But this should go into a later PR and not hold up merging this update.
>
> _Originally posted by @jandubois in https://github.com/lima-vm/lima/pull/4989#pullrequestreview-4719367979_
>

No documentation file, test, or entry point is named in the issue. Locate the existing CI guidance and review how maintainers rerun jobs; done means the documentation explains flaky CI behavior and when rerunning jobs may be appropriate.

Written by the indexing model from the issue text.