Update ci.yml

[benjaminrwilson]

PR Summary

• Tagged releases aren't properly uploaded currently (we must manually push to PyPI). The aim of this PR is to (1). periodically push to the test PyPI index and (2). properly build and push the source distribution + wheels.
• Removes pytype --- slows down CI and doesn't fully support our build matrix.

Testing

In order to ensure this PR works as intended, it is:

• unit tested.
• other or not applicable (additional detail/rationale required)

Compliance with Standards

As the author, I certify that this PR conforms to the following standards:

• Code changes conform to PEP8 and docstrings conform to the Google Python style guide.
• A well-written summary explains what was done and why it was done.
• The PR is adequately tested and the testing details and links to external results are included.