docs: remove incorrectedly reverted deleted content

[bearomorphism]

See https://github.com/commitizen-tools/commitizen/pull/1236/files#diff-4795f0c47daaacdcc54b5ec64b46df2c416b04abcbba2ef60590ad23ae025a5a

The added content was moved to python_class.md.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.84%. Comparing base (120d514) to head (a38c32b).
⚠️ Report is 898 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1743      +/-   ##
==========================================
+ Coverage   97.33%   97.84%   +0.51%     
==========================================
  Files          42       60      +18     
  Lines        2104     2604     +500     
==========================================
+ Hits         2048     2548     +500     
  Misses         56       56              

Flag	Coverage Δ
unittests	97.84% <ø> (+0.51%)	⬆️

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