ci/container: Drop unnecessary variables for image paths

Some (and not all) MESA_IMAGE_PATH and MESA_BASE_IMAGE entries used
variables set in image-tags.yml, but these weren't too useful.
Drop them for simplicity.

Signed-off-by: Valentine Burley <valentine.burley@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34405>
2 files changed