[FSDP] No need for list() in _get_shard (#66957)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66957
chunk appears to return a tuple which is enough given that we just
index to the right chunk and discard the rest.
ghstack-source-id: 141391149
Test Plan: CI
Reviewed By: mrshenli
Differential Revision: D31780799
fbshipit-source-id: fdb1b77fffa916328e14a4cd692b5241ae46a514
