www/gitlab: security and patch update to 18.9.2

Changes: https://about.gitlab.com/releases/2026/03/11/patch-release-gitlab-18-9-2-released/
Security: 0236eab0-1d62-11f1-88f8-2cf05da270f3
(cherry picked from commit be0fcc223124379be8b268089db49c45f38bd408)