mypy

a5e316ea - Do not import `TypedDict` from `mypy-extensions`, use `typing-extensions` (#15494)

Do not import `TypedDict` from `mypy-extensions`, use `typing-extensions` (#15494) All recent versions (declared in `setup.py`) have `TypedDict` there. So, no need to use `mypy-extensions` here. (crossref: found while working on https://github.com/typeddjango/django-stubs/pull/1566)