CompatHelper: bump compat for Trixi to 0.9 for package LibTrixi.jl, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Trixi package from 0.7.16, 0.8 to 0.7.16, 0.8, 0.9 for package LibTrixi.jl.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.27%. Comparing base (11e7a60) to head (a90c782).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #208   +/-   ##
=======================================
  Coverage   80.27%   80.27%           
=======================================
  Files          19       19           
  Lines         715      715           
  Branches       50       50           
=======================================
  Hits          574      574           
  Misses        137      137           
  Partials        4        4           

Flag	Coverage Δ
unittests	80.27% <ø> (ø)

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