[typing] Pyre fixes for remote_module (#59046)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59046
Correcting type hint for _RemoteModule to pass Pyre checks.
Test Plan: N/A
Reviewed By: walterddr, SciPioneer
Differential Revision: D28725237
fbshipit-source-id: 1ca714bbf1a597a29850f70bac826a0c95a4019f
