CI: Use a token for non-fork Codecov uploads

[DilumAluthge]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.45%. Comparing base (097adec) to head (009ebc4).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
+ Coverage   95.00%   95.45%   +0.45%     
==========================================
  Files           1        1              
  Lines          20       22       +2     
==========================================
+ Hits           19       21       +2     
  Misses          1        1              

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