Use a fixed version of the GitLab chart for Review Apps

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab/ci/review.gitlab-ci.yml

@@ -97,7 +97,7 @@ schedule:review-build-cng:
   variables:
     HOST_SUFFIX: "${CI_ENVIRONMENT_SLUG}"
     DOMAIN: "-${CI_ENVIRONMENT_SLUG}.${REVIEW_APPS_DOMAIN}"
-    GITLAB_HELM_CHART_REF: "master"
+    GITLAB_HELM_CHART_REF: "v2.3.7"
     GITLAB_EDITION: "ce"
   environment:
     name: review/${CI_COMMIT_REF_NAME}