ci: Don't install gems in frontend jobs

This regression was introduced on 2021-10-13 by
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/70000/diffs#bc318a83678054413c272445fd279ef503d73f0f_172_198Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab/ci/frontend.gitlab-ci.yml

@@ -193,9 +193,7 @@ graphql-schema-dump:
     # Disable warnings in browserslist which can break on backports
     # https://github.com/browserslist/browserslist/blob/a287ec6/node.js#L367-L384
     BROWSERSLIST_IGNORE_OLD_DATA: "true"
-    SETUP_DB: "false"
   before_script:
-    - !reference [.default-before_script, before_script]
     - *yarn-install
   stage: test