[CircleCI] Delete docker image after testing (#40917)
Summary:
Needed maintenance step to avoid running out of disk space on RocM testers
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40917
Differential Revision: D22385844
Pulled By: malfet
fbshipit-source-id: b6dc9ba888a2e34c311e9bf3c8b7b98fa1ec5435
