www/gitlab: security and patch update to 18.3.4
Changes: https://about.gitlab.com/releases/2025/10/08/patch-release-gitlab-18-4-2-released/
Security: 87fdaf3c-a5b5-11f0-98b5-2cf05da270f3
(cherry picked from commit 8d6e8a6e3764e1d9ce8a2b2e19509532fc913bdf)