Improve paths filtering of docs CI job (backport #2367)

[mergify]

ros-controls/control_toolbox#424

---

This is an automatic backport of pull request #2367 done by Mergify.

[mergify]

Cherry-pick of c1386c5 has failed:

On branch mergify/bp/humble/pr-2367
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit c1386c5.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .github/workflows/humble-check-docs.yml
	modified:   .github/workflows/jazzy-check-docs.yml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/rolling-check-docs.yml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally