Use a fixed version of the GitLab charts in our Review App deployments

Since we're using the master GitLab chart, we sometimes have failures that are unavoidable e.g. #34207 (closed) (where a deprecation warning is preventing Review App deployments entirely, which is good in a production environment, but would actually make the Review App deployments success rate go down in our case (which is a problem because we have a high target: gitlab-com/www-gitlab-com!32252 (comment 231071427)), and the only thing we can do is reacting to this change, and wait for people to rebase their branch upon the fixed master).

If we want to hit 99% success rate, we should use a released/fixed version of the chart.