message: Document how benchmark results can be pruned from S3
diff: @@ -74,3 +74,11 @@ To plot final task accuracies in a group of tasks use
  $ pull_results
  $ plot_final_task_accuracies --group_name=GROUP_NAME
  ```
  +
  +## Removing obsolete plots
  +
  +To remove **all** plots from S3:
  +
  +```shell
  +aws s3 rm --recursive s3://xain-results
  +```
  