Add missing AWS region env to workflows (#510)
Summary:
`boto3` needs these to run, should fix https://github.com/pytorch/benchmark/runs/3967582406?check_suite_focus=true
Pull Request resolved: https://github.com/pytorch/benchmark/pull/510
Reviewed By: xuzhao9
Differential Revision: D31835754
Pulled By: driazati
fbshipit-source-id: 0173b3df48b6b16fdfb27675e9b9c021339c3a42
