TypedDict support breaks using postponed evaluation of annotations

[sg495]

Using postponed evaluation of annotations from PEP-563 breaks TypedDict support introduced in v1.2.0:

>>> from __future__ import annotations
>>> from typing import TypedDict
>>> class MyDict(TypedDict):
>>>     x: int
>>> validate({"x": 2}, MyDict)
ValueError: Type alias 'int' is not known. Perhaps set it with validation_aliases(int=...)?

The issues is a direct access to t.__annotations__ in _validate_typed_dict, which use get_type_hints(t) instead.