gitlab-ci: Update required libdrm version

gitlab-ci: Update required libdrm version

Commit 9edcce2a32ed bumped the required libdrm-amdgpu version to
2.4.100. Update the version we use in our CI scripts to avoid CI
build failures.

Also bump the debian image name for this change to take effect.
Note that amdgpu is only built with the debian-buster image,
so only this image requires an update.

Fixes: 9edcce2a ("ac: get tcc_harvested from the kernel")
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>