drm/ci: update link to Gitlab server

Before building an image, the build script looks to see if there are fixes
to apply from an upstream repository. The link for the upstream repository
git://anongit.freedesktop.org/drm/drm

 became obsolete with the move to
Gitlab server in March 2024. Until recently, this obsolete link was
harmless because anongit would at least respond that there were no such
fixes available. In the last few days anongit has stopped responding to
requests causing the build script to hang indefinitely.

Update the link from anongit to the Gitlab server to prevent the build
script from hanging indefinitely.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240717235221.64629-1-deborah.brouwer@collabora.com