use GitHub token to authenticate downloads in CI

[ranocha]

See trixi-framework/Trixi.jl#2415. This will be active when the new version of Trixi.jl is released, which should occur in a few minutes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.17%. Comparing base (ae36086) to head (34ffb58).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #103   +/-   ##
=======================================
  Coverage   99.17%   99.17%           
=======================================
  Files          77       77           
  Lines        3635     3635           
=======================================
  Hits         3605     3605           
  Misses         30       30           

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[andrewwinters5000]

Thanks for taking care of this!