Run the review-docs-cleanup jobs for gitlab-org repos only

Run the review-docs-cleanup jobs only for the gitlab-org group to avoid failing tests from forks, like for review-docs/review-docs-deploy (!20327 (merged)).

Case(s)

In the forked repo from gitlab-org, we will see such an error:

• https://gitlab.com/tnir/gitlab-ce/pipelines/29195445

cf. !20327 (merged)