Limit sphinx-autodoc-typehints upper bound

[ascillitoe]

Limit sphinx-autodoc-typehints to <1.19.3 due to tox-dev/sphinx-autodoc-typehints#259 and tox-dev/sphinx-autodoc-typehints#260.

alibi equivalent: SeldonIO/alibi#790

[ascillitoe]

@jklaise the docs CI is now passing 👍🏻

[codecov-commenter]

Codecov Report

Merging #633 (af3be06) into master (2683721) will decrease coverage by 0.07%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #633      +/-   ##
==========================================
- Coverage   77.96%   77.88%   -0.08%     
==========================================
  Files         123      123              
  Lines        8749     8714      -35     
==========================================
- Hits         6821     6787      -34     
+ Misses       1928     1927       -1     

Flag	Coverage Δ
macos-latest-3.10.6	?
ubuntu-latest-3.10.6	?
ubuntu-latest-3.7	77.75% <ø> (ø)
ubuntu-latest-3.8	77.79% <ø> (ø)
ubuntu-latest-3.9	77.79% <ø> (ø)
windows-latest-3.9	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
alibi_detect/utils/frameworks.py	87.50% <0.00%> (-4.17%)	⬇️
alibi_detect/utils/missing_optional_dependency.py	94.28% <0.00%> (-0.16%)	⬇️
alibi_detect/datasets.py	68.55% <0.00%> (-0.14%)	⬇️
alibi_detect/saving/schemas.py	99.20% <0.00%> (-0.05%)	⬇️
alibi_detect/utils/fetching/fetching.py	0.00% <0.00%> (ø)
alibi_detect/cd/base.py	91.14% <0.00%> (+0.21%)	⬆️
alibi_detect/od/vae.py	90.36% <0.00%> (+1.07%)	⬆️