Fixup: rename BatchedTensorKey to Batched (#38798)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38798
This makes it more in-line with the other keys in the file
(DispatchKey.h).
Test Plan: Imported from OSS
Differential Revision: D21691789
Pulled By: zou3519
fbshipit-source-id: 8d8b902360c0238f67bd0e58f9d969cec4b63320
