[JIT] fix alias assertion (#33952)
Summary:
This bug has been hit a couple times recently. We need to handle all bivariant types, not just optional, when asserting mutability/immutability of pointed-to elements in alias analysis.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33952
Differential Revision: D20166025
Pulled By: eellison
fbshipit-source-id: cf3df9897a639641ef8303a08ba2b13523d01ef1
