Updated pymc.InverseGamma docstring

[areding]

• [x ] right before it's ready to merge, mention the PR in the RELEASE-NOTES.md

This will update the pymc.InverseGamma docstring, relating to #5459.

[codecov]

Codecov Report

Merging #5499 (c12fa70) into main (6857729) will decrease coverage by 4.55%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5499      +/-   ##
==========================================
- Coverage   81.44%   76.89%   -4.56%     
==========================================
  Files          81       81              
  Lines       14204    14204              
==========================================
- Hits        11569    10922     -647     
- Misses       2635     3282     +647     

Impacted Files	Coverage Δ
pymc/distributions/continuous.py	97.13% <ø> (-0.10%)	⬇️
pymc/ode/utils.py	17.85% <0.00%> (-82.15%)	⬇️
pymc/ode/ode.py	24.24% <0.00%> (-60.61%)	⬇️
pymc/step_methods/mlda.py	50.96% <0.00%> (-45.43%)	⬇️
pymc/step_methods/metropolis.py	48.93% <0.00%> (-34.05%)	⬇️
pymc/step_methods/elliptical_slice.py	33.33% <0.00%> (-33.34%)	⬇️
pymc/tuning/scaling.py	35.18% <0.00%> (-24.08%)	⬇️
pymc/sampling.py	73.43% <0.00%> (-13.35%)	⬇️
pymc/step_methods/hmc/quadpotential.py	72.81% <0.00%> (-7.74%)	⬇️
pymc/step_methods/arraystep.py	86.52% <0.00%> (-6.39%)	⬇️
... and 10 more