[AIRFLOW-6511] Remove BATS docker containers (#7103)
[AIRFLOW-6511] Remove BATS docker containers (#7103)

The containers were not removed and you have to remove them
with `dockery system prune`. The --rm flag is added.

(cherry picked from commit 0ec7232e65b67a6f37fd19471e7f744201fe0464)

owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow