Transition this repo (and other asdf-format ones) to trusted publishing

[braingram]

Using trusted publishing will:

• allow removal of the publishing token secret
• be compatible with the likely future where trusted publishing is the only option

https://docs.pypi.org/trusted-publishers/ has some general information.
Given that we use the same workflow as asdf-astropy:
https://github.com/asdf-format/asdf/blob/main/.github/workflows/build.yml
this PR may be a useful example of how to update the current workflows:
astropy/asdf-astropy#322