add-license-headers is changing special characters

[klmcadams]

The hook is incorrectly writing special characters with fileinput when using python 3.9

https://github.com/ansys/pyadditive/blob/main/src/ansys/additive/core/microstructure.py

[RobPasMue]

Make sure to use the same encoding. Seems to me like that's the main issue. The "micro" symbol is not UTF-8, but UTF-16 probably... you'll need to double check