Update docs/customization/python_class.md

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

Author: bearomorphism

docs/customization/python_class.md

@@ -89,7 +89,7 @@ So in the end, we would have
     ├── cz_jira.py
     └── setup.py
 
-And that's it. You can install it without uploading to pypi by simply
+And that's it. You can install it without uploading to PyPI by simply
 doing `pip install .`
 
 If you feel like it should be part of this repo, create a PR.