Extend the systemd auto-update service to prune images after an update
has run. As reported by a user [1], auto updates can over time cause
the disk to run out of space. With Edge being a target use case, we
need to make sure that systems can run without much supervision, so
let's make sure to run `podman image prune` to clean up dangling images.
[1] https://twitter.com/r_isc_y/status/1388981737011793921Fixes: #10190
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
9738f63bac