BetaBinomial variance is not correctly described

[soma2000-lang]

Fixes #6495
@OriolAbril @ricardoV94 @larryshamalama

[codecov]

Codecov Report

Merging #6516 (995eddd) into main (ac9652e) will decrease coverage by 9.60%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6516      +/-   ##
==========================================
- Coverage   94.82%   85.23%   -9.60%     
==========================================
  Files         148      146       -2     
  Lines       27818    27807      -11     
==========================================
- Hits        26379    23701    -2678     
- Misses       1439     4106    +2667     

Impacted Files	Coverage Δ
pymc/distributions/discrete.py	99.22% <ø> (ø)
pymc/tests/logprob/test_utils.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_cumsum.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_mixture.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_abstract.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_rewriting.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_joint_logprob.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_composite_logprob.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/logprob/test_transforms.py	0.00% <0.00%> (-99.76%)	⬇️
pymc/tests/distributions/test_truncated.py	0.00% <0.00%> (-99.49%)	⬇️
... and 52 more