build: Update codecov and use token

[arbrandes]

Update codecov to the latest version and start using the org-wide token for uploads.

See openedx/wg-frontend#179

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.18%. Comparing base (dedcb14) to head (74776b3).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #485      +/-   ##
==========================================
- Coverage   89.25%   89.18%   -0.07%     
==========================================
  Files         246      246              
  Lines        4475     4505      +30     
  Branches      917      920       +3     
==========================================
+ Hits         3994     4018      +24     
- Misses        454      456       +2     
- Partials       27       31       +4     

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[bszabo]

@arbrandes Though the CI build for this PR reported itself free of errors, the last few lines in the release dropdown here indicate that no new version was released, hence your change's impact on release was not tested. The PR immediately following yours then had fatal release errors, and its possible that PR 484 introduced the problem.