Add a comment about updating tags in .gitlab-ci/image-tags.yml to the
.gitlab-ci/container/create-android-cross-file.sh as it is not immediate
that it gets called from .gitlab-ci/container/debian/android_build.sh
which also requires to update DEBIAN_BUILD_TAG.
Reviewed-by: Valentine Burley <valentine.burley@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36710>