Simplify pypi release action

[korikuzma]

          is there a reason we aren't just spec'ing the branch name under the workflow triggers?

edit: or something like if: github.ref == 'refs/heads/main' under the job itself

Originally posted by @jsstevenson in #508 (comment)

[korikuzma]

We tried doing this in #508 and #509 but the jobs were skipped. https://github.com/ga4gh/vrs-python/actions/runs/13289616067

[korikuzma]

#616 we removed this check