Numba backend: set parallel=False by default for n_dims==0

[slayoo]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 87.45%. Comparing base (d1360ae) to head (b1dbcad).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
PySDM/backends/numba.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1967      +/-   ##
==========================================
- Coverage   87.46%   87.45%   -0.02%     
==========================================
  Files         429      429              
  Lines       11140    11140              
==========================================
- Hits         9744     9742       -2     
- Misses       1396     1398       +2     

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