Update gitlab runners to v15.9.1
This upgrades the version of the gitlab cloud runners to 15.9.1 to align it with GitLab server version.
Bug: T335784
How to register an account on GitLab. To prevent spam, new accounts are locked until approved by an admin or the approver bot. You can also file an unlock request to expedite access.
Support: mw:GitLab, how to host a project on GitLab, #wikimedia-gitlab on libera.chat, #GitLab on Phabricator.
This upgrades the version of the gitlab cloud runners to 15.9.1 to align it with GitLab server version.
Bug: T335784