www/gitlab: security and patch update to 18.1.2

Changes: https://about.gitlab.com/releases/2025/07/09/patch-release-gitlab-18-1-2-released/
Security: 20823cc0-5d45-11f0-966e-2cf05da270f3
(cherry picked from commit 6962131cd928e4801aabadcfeba3da4f2ea8df65)