Update python-gitlab from 4.x to 5.x to fix AttributeError with __annotations__ when running on Python 3.14. The 4.x series is incompatible with Python 3.14 due to changes in how class annotations are handled. Signed-off-by: Christian Gmeiner <cgmeiner@igalia.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38123>