Disable signups for review apps
Disables signups in the review app once its been installed.
This is pulled from the work done here in the gitlab review apps: https://gitlab.com/gitlab-org/gitlab/-/blob/99ba0b38f504342ce8654cc1378b4e199cacef01/scripts/review_apps/review-apps.sh#L137
And is mostly kept the same, with the exception of the removal of the jq check at the end, as we don't have jq available in our current ci image here.
Closes https://gitlab.com/gitlab-org/charts/gitlab/-/issues/2272
Edited by DJ Mountney