Allow fewer arguments than the max in ArgumentSpec (#17826)
Summary:
Fixes #17558
The flattened tuple `Optional[Tuple[int, int]]` could either result in 1 (`None`) or 2 (`int` and `int`) values, so allow this case in `ArgumentSpec`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17826
Differential Revision: D14415290
Pulled By: driazati
fbshipit-source-id: 971bfa39502cfb8f08a991f16ffed6d138e48dc9
