CompatHelper: bump compat for Trixi to 0.8 for package LibTrixi.jl, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the Trixi package from 0.7.16 to 0.7.16, 0.8 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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.27%. Comparing base (fe66f83) to head (71d52f2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #195 +/- ## ======================================= Coverage 80.27% 80.27% ======================================= Files 19 19 Lines 715 715 Branches 50 50 ======================================= Hits 574 574 Misses 137 137 Partials 4 4 ``` | [Flag](https://app.codecov.io/gh/trixi-framework/libtrixi/pull/195/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/trixi-framework/libtrixi/pull/195/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | `80.27% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework#carryforward-flags-in-the-pull-request-comment) to find out more.

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