clearing up after docker

 Via https://stackoverflow.com/questions/76833923/safe-way-to-clean-var-lib-docker

/var/lib/docker was using up 16 GB. 

sudo docker system prune --all --volumes

WARNING! This will remove:

  - all stopped containers
  - all networks not used by at least one container
  - all anonymous volumes not used by at least one container
  - all images without at least one container associated to them
  - all build cache

Total reclaimed space: 7.794GB