TST: temporary changing git actions

[Gui-FernandesBR]

I am removing macOS + python 3.8 from the tests matrix.

This will avoid a hdf5 error that is preventing us to install rocketpy on macOS using python 3.8

For future reference: h5py/h5py#2408

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.03%. Comparing base (bb0f46a) to head (3bf219a).
Report is 13 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #590      +/-   ##
===========================================
+ Coverage    72.99%   73.03%   +0.03%     
===========================================
  Files           59       57       -2     
  Lines         9543     9596      +53     
===========================================
+ Hits          6966     7008      +42     
- Misses        2577     2588      +11     

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