Install Docker deb package using Ubuntu repository

dylan/minersrealm-panel#1 (closed) is caused by an outdated Docker version. This appears to be caused by the Docker Salt forumla installing the binary by downloading it directly from the internet. The version currently defined in the Docker Salt formula defaults.yaml is 19.03.9 which is a version from early 2019: https://gitlab.dylanwilson.dev/infrastructure/salt-formulas/docker-formula/-/blob/master/docker/defaults.yaml#L34.

The solution is to either specify a newer version in pillars (which would require updating the pillars each time to install a new Docker version) or, the preferable solution, to install Docker via Docker's Ubuntu repositories which would mean Docker would be updated when running apt upgrade.

This requires changes in this repository to .kitchen.yml to include use_upstream: repo in the testing pillars to replicate the changes in the production pillars.