mypy.ini file python_version says DIGIT.DIGIT which is wrong for 3.10

**Documentation**
The mypy.ini file [python_version](https://mypy.readthedocs.io/en/stable/config_file.html#confval-python_version) documentation says that:
> The string should be in the format DIGIT.DIGIT

But that's not right for python 3.10 which has two digits after the dot