Clean up some type annotations in android (#49944)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49944
Upgrades type annotations from Python2 to Python3
Test Plan: Sandcastle tests
Reviewed By: xush6528
Differential Revision: D25717539
fbshipit-source-id: c621e2712e87eaed08cda48eb0fb224f6b0570c9
