ci: Disable broken MR check in sanity job

GitLab recently changed the required permissions for the
are-developers-allowed-to-push-to-my-MR check:
https://gitlab.freedesktop.org/freedesktop/ci-templates/-/issues/81

Until that’s resolved, disable the check - it’s mostly obsolete anyway.

Signed-off-by: Valentine Burley <valentine.burley@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37782>

.gitlab-ci.yml

@@ -391,7 +391,7 @@ sanity:
     GIT_STRATEGY: none
   script:
     # ci-fairy check-commits --junit-xml=check-commits.xml
-    - ci-fairy check-merge-request --require-allow-collaboration --junit-xml=check-merge-request.xml
+    # ci-fairy check-merge-request --require-allow-collaboration --junit-xml=check-merge-request.xml
     - |
       set -eu
       image_tags=(