pass `None` instead of `False` inside `Adam.__setstate__` (#93289)
with https://github.com/pytorch/pytorch/commit/a061f139dccb5f56c9d14e25ef54ff821b4dd3c8, `fused`'s type hint is `Optional[bool]` and its default value is `None`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93289
Approved by: https://github.com/janeyx99, https://github.com/Skylion007
