Update Test-coverage.yaml

[jgabry]

Submission Checklist

• Run unit tests
• Declare copyright holder and agree to license (see below)

Summary

It doesn't seem like codecov is properly tracking the coverage for the package. This PR updates the test coverage yaml file to be close to the latest from r-lib/actions. We can't use exactly their file, but this tries to get as close as possible while keeping the custom stuff we need for cmdstanr.

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Columbia University

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.22%. Comparing base (5013fcf) to head (b9f082c).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1092      +/-   ##
==========================================
+ Coverage   85.45%   87.22%   +1.76%     
==========================================
  Files          14       14              
  Lines        4896     5973    +1077     
==========================================
+ Hits         4184     5210    +1026     
- Misses        712      763      +51     

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[jgabry]

Will merge since this doesn't change any code in the package.