Fix relative links to GitLab subcharts
Fix some links that broke the builds of the gitlab-docs project https://gitlab.com/gitlab-com/gitlab-docs/-/jobs/160996096.
Introduced in https://gitlab.com/charts/gitlab/merge_requests/676/diffs#801242868529a9e543ce40df851490d6c4d3e4d4.
We need to catch those earlier https://gitlab.com/charts/gitlab/merge_requests/679.
Edited by Achilleas Pipinellis