mypy allows TypedDict classes with metaclasses

[sobolevn]

from typing import TypedDict

class A(type): ...

class Foo(TypedDict, metaclass=A):
   x: int

This code raises no errors in mypy. But, PEP says: https://peps.python.org/pep-0589/

Specifying a metaclass is not allowed.

I am working on a PR.

[sobolevn]

Closed by #16438