drm/ci: docs: add step about how to request privileges

Clarify the procedure developer must follow to request privileges to
run tests on Freedesktop gitlab CI.

This measure was added to avoid untrusted people to misuse the
infrastructure.
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Reviewed-by: David Heidelberg <david.heidelberg@collabora.com>
Link: https://lore.kernel.org/r/20231024004525.169002-11-helen.koike@collabora.comSigned-off-by: Maxime Ripard <mripard@kernel.org>

Documentation/gpu/automated_testing.rst

@@ -99,10 +99,13 @@ https://gitlab.freedesktop.org/janedoe/linux/-/settings/ci_cd), change the
 CI/CD configuration file from .gitlab-ci.yml to
 drivers/gpu/drm/ci/gitlab-ci.yml.
 
-3. Next time you push to this repository, you will see a CI pipeline being
+3. Request to be added to the drm/ci-ok group so that your user has the
+necessary privileges to run the CI on https://gitlab.freedesktop.org/drm/ci-ok
+
+4. Next time you push to this repository, you will see a CI pipeline being
 created (eg. https://gitlab.freedesktop.org/janedoe/linux/-/pipelines)
 
-4. The various jobs will be run and when the pipeline is finished, all jobs
+5. The various jobs will be run and when the pipeline is finished, all jobs
 should be green unless a regression has been found.