Cleanup examples

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 69.92%. Comparing base (f7906a5) to head (d91177c).

Files	Patch %	Lines
src/general/semidiscretization.jl	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #592 +/- ## ========================================== - Coverage 69.94% 69.92% -0.03% ========================================== Files 86 86 Lines 5118 5120 +2 ========================================== Hits 3580 3580 - Misses 1538 1540 +2 ``` | [Flag](https://app.codecov.io/gh/trixi-framework/TrixiParticles.jl/pull/592/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/trixi-framework/TrixiParticles.jl/pull/592/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | `69.92% <33.33%> (-0.03%)` | :arrow_down: | 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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[svchb]

Have you checked that all these trixi_include commands give you the simulations you want? It's easy to miss something and end up with an incorrect simulation setup.

yes I have just scrolled through again. As far as I know everything should be fine. At least all of the values that are defined are used.