`NewType` documentation is incorrect

[AlexWaygood]

The documentation for NewType at https://mypy.readthedocs.io/en/stable/more_types.html#newtypes states:

...the typing module provides a helper function NewType that creates simple unique types with almost zero runtime overhead.

However, as the cpython documentation for NewType` states:

Changed in version 3.10: NewType is now a class rather than a function. There is some additional runtime cost when calling NewType over a regular function. However, this cost will be reduced in 3.11.0.

In Python >=3.10, NewType is a class rather than a function, meaning the mypy documentation is now incorrect.

I'm not immediately sure how it could be rewritten in a more accurate way that is still concise, however.

[JelleZijlstra]

We can just replace "function" with "object". The overhead is still tiny, and it doesn't matter to readers of the mypy documentation exactly how NewType is implemented.

[AlexWaygood]

We can just replace "function" with "object". The overhead is still tiny, and it doesn't matter to readers of the mypy documentation exactly how NewType is implemented.

Makes sense, thanks!