Fixes __init__ of typing.NamedTuple - #6080

I think @srittau accidentally edited your comment instead of responding to your questions. I restored your original comment (approximately, couldn't find the raw markdown). Here are my thoughts:

(Iterable[Tuple[str, Any]] and kwargs: Any) or (Iterable[Tuple[str, type]] and kwargs: type)

I'd say the former. Not all acceptable types are actually types.

Do we need fields: None = ... in the second overload?

Yes, because fields=None is legal at runtime.

@JelleZijlstra done! I agree with fields=None and type after writting so many tests in python/mypy#11206 😆

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

Thanks everyone! 🎉