Stop using CODECOV_TOKEN

[dfed]

Forked repos should be able to contribute and have CI succeed. Example failure: https://github.com/dfed/SafeDI/actions/runs/12676458517/job/35331202575

I have made the token not required in Codecov

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.91%. Comparing base (b6d4ccb) to head (3594d26).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #144      +/-   ##
==========================================
- Coverage   99.91%   99.91%   -0.01%     
==========================================
  Files          32       32              
  Lines        3467     3465       -2     
==========================================
- Hits         3464     3462       -2     
  Misses          3        3              

see 1 file with indirect coverage changes