chore: fix release workflow

[WilliamBergamin]

Summary

In #72 we introduced a simplified release flow, it was in a broken state, these changes should remedy the issue

Testing

Merge this branch then manully trigger the workflow from https://github.com/slackapi/python-slack-hooks/actions/workflows/pypi-release.yml

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@57c5e39). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #73   +/-   ##
=======================================
  Coverage        ?   94.68%           
=======================================
  Files           ?       11           
  Lines           ?      207           
  Branches        ?        0           
=======================================
  Hits            ?      196           
  Misses          ?       11           
  Partials        ?        0           

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