www/gitlab: update to 17.6.0
Changes: https://gitlab.com/gitlab-org/gitlab/-/blob/master/CHANGELOG.md?expanded=true&viewer=simple
Changes: https://about.gitlab.com/releases/2024/11/21/gitlab-17-6-released/
(cherry picked from commit 2c08bdde941541c19d159fe8f51cfc01085c744a)