.gitlab-ci.yml: update Docker image to use
We have a new Docker image, updated with the new requirements from
bcd15aa08aab1e8292b93995c44dc765a9801632 ("support/docker: add
python3-magic"), but also with an updated Debian Bullseye
installation. Let's use it.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>