mypy allows `TypedDict` classes with metaclasses

```python
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.