[infrastructure] Update Codecov usage

[uilianries]

Similar to taocpp/PEGTL#374

@ColinH @d-frey I don't access to https://github.com/taocpp/config settings, so I can't add the Codecov secret Token.

Could you please add it? Need to copy the token listed in https://app.codecov.io/gh/taocpp/config/config/general

Then add it to https://github.com/taocpp/config/settings/secrets/actions by clicking on "New repository secret". The expected variable name is CODECOV_TOKEN.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.84%. Comparing base (b8406d2) to head (9de5b6b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
- Coverage   90.42%   82.84%   -7.59%     
==========================================
  Files          69       69              
  Lines        1745     1760      +15     
  Branches        0      158     +158     
==========================================
- Hits         1578     1458     -120     
+ Misses        167      166       -1     
- Partials        0      136     +136     

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