__bool__: add NoReturn to flag its use statically

[Andrej730]

Currently pyright already flags the use of __bool__ for a in the snippet below as an issue
Adding explicit NoReturn return type annotation to allow other type checkers (e.g. mypy with --warn-unreachable) to flag it too.

class A:
    def __bool__(self):
        raise TypeError


def test(a: A) -> None:
    if a:
        print("42")
    print("32")

[Andrej730]

@travisjungroth Hi! Can you please take a look?