Update docs/customization/python_class.md

Co-authored-by: Wei Lee <weilee.rx@gmail.com>

Author: bearomorphism

docs/customization/python_class.md

@@ -4,7 +4,7 @@ The basic steps are:
 
 1. Inheriting from `BaseCommitizen`.
 2. Give a name to your rules.
-3. Create a python package using `setup.py`, `poetry`, etc.
+3. Create a Python package using proper [build backend](https://packaging.python.org/en/latest/glossary/#term-Build-Backend)
 4. Expose the class as a `commitizen.plugin` entrypoint.
 
 Check an [example][convcomms] on how to configure `BaseCommitizen`.