Update `rapids-upload-to-anaconda` Error Handling (#25)
In a recent GitHub Actions run ([link](https://github.com/rapidsai/rapids-cmake/actions/runs/3413106288/jobs/5679670752#step:6:11)), the `rapids-upload-to-anaconda` script failed due to missing AWS credentials. However, since the bash error handling wasn't configured properly, the GH Action run was reported as a success.
This PR updates the script to ensure that this issue doesn't happen again.
Note that `inherit_errexit` ([link](https://saveriomiroddi.github.io/Additional-shell-options-for-non-trivial-bash-shell-scripts/#inherit_errexit)) would also work for this use case, but it's only supported on `bash` versions `4.4+` and `centos7` has `bash` version `4.2`. So that option was skipped for this situation.
