www/gitlab: security and patch update to 18.9.1

Changes: https://about.gitlab.com/releases/2026/02/25/patch-release-gitlab-18-9-1-released/
Security: 102a03c9-1316-11f1-93ca-2cf05da270f3
(cherry picked from commit b83e3292e93243502853e2fafa81d8de3b33089d)