ci: remove Docker containers after running builds

Run `docker run` with `--rm` to remove contaners after running
a container-based build.
These containers are never reused, so there's no reason to keep them.
Instead, a new container is created for each build.
Not removing them results in wasting disk space on CI runners.

NO_DOC=ci
NO_CHANGELOG=ci
NO_TEST=ci

(cherry picked from commit 065c2874)