Fix class_loader warnings in pilz unit tests

[todoubaba]

Description

When running pilz unit tests, class_loader reports the following warning:

Warning: class_loader.ClassLoader: SEVERE WARNING!!! Attempting to unload library while objects created by this loader exist in the heap! You should delete your objects before attempting to unload the library or destroying the ClassLoader. The library will NOT be unloaded.

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (4476fb6) 50.72% compared to head (700fbbb) 50.71%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2296      +/-   ##
==========================================
- Coverage   50.72%   50.71%   -0.00%     
==========================================
  Files         386      386              
  Lines       31914    31914              
==========================================
- Hits        16184    16181       -3     
- Misses      15730    15733       +3     

see 1 file with indirect coverage changes

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[sjahr]

Thanks for providing this fix!