Numba warning fix

[selmanozleyen]

Fixes: #994

Without the fix this is the warning I get in a notebook:

[/Users/selman.ozleyen/mambaforge/envs/squidpy/lib/python3.11/site-packages/numba/parfors/parfor.py:2395](https://file+.vscode-resource.vscode-cdn.net/Users/selman.ozleyen/mambaforge/envs/squidpy/lib/python3.11/site-packages/numba/parfors/parfor.py:2395): NumbaPerformanceWarning: 
prange or pndindex loop will not be executed in parallel due to there being more than one entry to or exit from the loop (e.g., an assertion).

File "/Users/selman.ozleyen/projects/squidpy/docs/notebooks/tutorials", line 31:
<source missing, REPL/exec in use?>

I don't think it is possible to add a test case because in theory that part of the code is unreachable

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 66.63%. Comparing base (4a632d6) to head (daf87bb).
Report is 197 commits behind head on main.

Files with missing lines	Patch %	Lines
src/squidpy/gr/_ligrec.py	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1002      +/-   ##
==========================================
- Coverage   69.99%   66.63%   -3.36%     
==========================================
  Files          39       40       +1     
  Lines        5532     6060     +528     
  Branches     1037     1015      -22     
==========================================
+ Hits         3872     4038     +166     
- Misses       1367     1662     +295     
- Partials      293      360      +67     

Files with missing lines	Coverage Δ
src/squidpy/gr/_ligrec.py	77.36% <50.00%> (-0.80%)	⬇️

... and 11 files with indirect coverage changes

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[ilan-gold]

To catch this sort of thing, the project should use the filterwarnings option and tests run so that warnings are treated as errors as is done in scanpy/anndata.

[ilan-gold]

So in this PR, you could also add to the pyproject.toml

[tool.pytest.ini_options]
filterwarnings = [ "error:NumbaPerformanceWarning" ]

or do it locally and go one-by-one and catch any others that exist

[ilan-gold]

I think it might need to be a double colon: https://docs.pytest.org/en/stable/how-to/capture-warnings.html#controlling-warnings sorry for the mistype