py23 module deprecation warning

Getting this message in the output window upon every RF open.
```
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Installing 'CornerTools' report:
  /Applications/RoboFont-4_4b2.app/Contents/Resources/lib/python3.9/fontTools/misc/py23.py:13: DeprecationWarning: The py23 module has been deprecated and will be removed in a future release. Please update your code.

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```