First argument of localdate() and localtime() should be Optional

[nuschk]

In timezone.pyi, instead of

def localtime(value: _AnyTime, timezone: Optional[tzinfo] = None) -> datetime: ...
def localdate(value: _AnyTime, timezone: Optional[tzinfo] = None) -> date: ...

these should quite simply be:

def localtime(value: Optional[_AnyTime] = None, timezone: Optional[tzinfo] = None) -> datetime: ...
def localdate(value: Optional[_AnyTime] = None, timezone: Optional[tzinfo] = None) -> date: ...

This is true for django >= 1.11, so well within the scope of django-stubs.

Oh, and thank you so much for this great package! <3

[sobolevn]

Yes, I confirm that this is true: https://github.com/django/django/blob/master/django/utils/timezone.py#L191-L211

[nuschk]

Thanks!