Change publish_test.yaml to not run on main

[chris-okuda]

Scope of changes

Change publish_test.yaml to not run on main because it will usually always fail since the version doesn't change from the PR upload that it was merged from, and this is only helpful for in a PR context anways. The test-pypi distribution will only happen on PRs.

Type of change

• bug fix
• new feature
• documentation
• other (describe)

Acceptance criteria

No special needs.

Author checklist

• I have manually tested the change and/or added automation in the form of unit tests or integration tests
• I have updated the dependencies list
• I have added new test fixtures as needed to support added tests
• I have added or updated the documentation
• Check this box if a reviewer can merge this pull request after approval (leave it unchecked if you want to do it yourself)

Reviewer(s) checklist

• Any new user-facing content that has been added for this PR has been QA'ed to ensure correct grammar, spelling, and understandability.
• To the best of my ability, I believe that this PR represents a good solution to the specified problem and that it should be merged into the main code base.