build(docs-infra): remove unused Docker artifacts when updating the preview server (#45895)

Update the `update-preview-server.sh` script that is used to update the
PR preview server to also remove unused Docker images and containers
after the update. This avoids having unused Docker artifacts grow
uncontrolled and fill up the VM disk drive.

PR Close #45895

aio/aio-builds-setup/scripts/update-preview-server.sh

@@ -67,5 +67,9 @@ readonly CONTAINER_NAME=aio
       --volume $HOST_LOGS_DIR:/var/log/aio \
       "$LATEST_IMAGE_NAME"
 
+  # Clean up unused docker containers and images (to reclaim space).
+  sudo docker container prune --force
+  sudo docker image prune --all --force
+
   echo "The new docker image has been successfully deployed."
 )