Added exit call to avoid problems when building documentation

[SRaimondi]

This PR adds an explicit exit call to the mapdl instance in the python documentation examples in order for it to not fail when building the documentation using the provided make.bat.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.97%. Comparing base (db5c9f4) to head (7e636ac).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ansys/acp/core/extras/example_helpers.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #745      +/-   ##
==========================================
- Coverage   94.99%   94.97%   -0.02%     
==========================================
  Files         109      109              
  Lines        5695     5696       +1     
  Branches      322      322              
==========================================
  Hits         5410     5410              
- Misses        284      285       +1     
  Partials        1        1              

Flag	Coverage Δ
direct-launch	91.57% <0.00%> (-0.02%)	⬇️
minimum-deps	93.18% <0.00%> (-0.02%)	⬇️
python-3.10	94.24% <0.00%> (-0.02%)	⬇️
python-3.11	94.17% <0.00%> (-0.02%)	⬇️
python-3.12	94.36% <0.00%> (-0.02%)	⬇️
server-2024R2	90.80% <0.00%> (-0.02%)	⬇️
server-2025R1	94.17% <0.00%> (-0.02%)	⬇️
server-2025R2	94.17% <0.00%> (-0.02%)	⬇️
server-latest	94.78% <0.00%> (-0.02%)	⬇️

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[greschd]

I think this should be added to all examples running MAPDL - you can search for launch_mapdl to find them.

[greschd]

@SRaimondi for the codecov check we can use our own judgement to ignore it - it will "fail" if the coverage reduces, or any of the changed lines is not covered in tests. But this can be caused by harmless changes like formatting, or here where the code is for the examples only.
The action will fail, but not block merging.