delete $ symbol, fix #353

[huangchieh]

I find it more convenient to copy the code without these $ symbols, and it also helps maintain consistency. I also think it might be a good idea to update these two wiki pages, though I couldn’t find the source documents in the repository.

1. https://github.com/Probe-Particle/ppafm/wiki/Install-ppafm#enable-gpugui-support
2. https://github.com/Probe-Particle/ppafm/wiki/For-Developers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.60%. Comparing base (c6e7e74) to head (a0f0d46).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #354      +/-   ##
==========================================
- Coverage   55.61%   55.60%   -0.01%     
==========================================
  Files          40       44       +4     
  Lines        6252     6262      +10     
==========================================
+ Hits         3477     3482       +5     
- Misses       2775     2780       +5     

Flag	Coverage Δ
python-3.10	55.60% <ø> (?)
python-3.11	55.57% <ø> (?)
python-3.12	55.57% <ø> (-0.04%)	⬇️
python-3.13	55.57% <ø> (?)
python-3.9	55.52% <ø> (?)

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[NikoOinonen]

@huangchieh Thanks, this is better.

I also think it might be a good idea to update these two wiki pages, though I couldn’t find the source documents in the repository.

I updated those pages as well. Unfortunately the wiki is not under the git repository, so external people cannot contribute to it.