Use generated version for __version__, remove old py2 compat code

[saimn]

No description provided.

[pllim]

Gonna kick off wheel job too, just in case. Thanks!

[codecov]

Codecov Report

Merging #149 (e1d71c5) into main (59b8d17) will increase coverage by 0.28%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##             main     #149      +/-   ##
==========================================
+ Coverage   89.14%   89.43%   +0.28%     
==========================================
  Files          23       23              
  Lines        1115     1098      -17     
==========================================
- Hits          994      982      -12     
+ Misses        121      116       -5     

Impacted Files	Coverage Δ
sphinx_automodapi/tests/helpers.py	100.00% <ø> (ø)
sphinx_automodapi/utils.py	90.82% <ø> (+2.22%)	⬆️
sphinx_automodapi/automodapi.py	93.75% <66.66%> (+0.45%)	⬆️
...hinx_automodapi/tests/test_autodoc_enhancements.py	95.00% <75.00%> (ø)
sphinx_automodapi/__init__.py	100.00% <100.00%> (ø)
sphinx_automodapi/automodsumm.py	85.62% <100.00%> (-0.05%)	⬇️
sphinx_automodapi/tests/test_automodapi.py	100.00% <100.00%> (+0.83%)	⬆️
sphinx_automodapi/tests/test_cases.py	100.00% <100.00%> (ø)

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[pllim]

LGTM. Nice clean-up!