Add polyagamma to requirements-dev.txt

[canyon289]

Local tests fail if this isn't installed, which makes development confusing until the dev figures this out

[codecov]

Codecov Report

Merging #5368 (ddd9fe8) into main (d52655d) will increase coverage by 3.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5368      +/-   ##
==========================================
+ Coverage   80.36%   83.43%   +3.06%     
==========================================
  Files          89      132      +43     
  Lines       14808    26042   +11234     
==========================================
+ Hits        11901    21728    +9827     
- Misses       2907     4314    +1407     

Impacted Files	Coverage Δ
pymc/parallel_sampling.py	86.71% <0.00%> (-1.00%)	⬇️
pymc/distributions/continuous.py	96.93% <0.00%> (-0.50%)	⬇️
pymc/distributions/__init__.py	100.00% <0.00%> (ø)
pymc/distributions/distribution.py	91.40% <0.00%> (ø)
pymc/tests/test_posteriors.py	100.00% <0.00%> (ø)
pymc/tests/test_shape_handling.py	93.11% <0.00%> (ø)
pymc/tests/test_func_utils.py	92.00% <0.00%> (ø)
pymc/tests/test_quadpotential.py	95.50% <0.00%> (ø)
pymc/tests/test_step.py	97.94% <0.00%> (ø)
pymc/tests/test_distributions_timeseries.py	54.83% <0.00%> (ø)
... and 38 more

[OriolAbril]

@canyon289 you should modify the conda envs with dev in their name. Then pre-commit automatically writes/updates requirements.txt. It doesn't work the other way around