Protect PyPI upload with CI environment

[brynpickering]

Reviewer checklist:

• [ ] Test(s) added to cover contribution
• [ ] Documentation updated
• [ ] Changelog updated
• [ ] Coverage maintained or improved

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e2e5077) 95.70% compared to head (36c0690) 95.70%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #547 +/- ## ======================================= Coverage 95.70% 95.70% ======================================= Files 24 24 Lines 3562 3562 Branches 775 710 -65 ======================================= Hits 3409 3409 Misses 87 87 Partials 66 66 ```