Update RNN op registration format (#43599)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/43599
Test Plan: Imported from OSS
Reviewed By: smessmer
Differential Revision: D23350223
Pulled By: iseeyuan
fbshipit-source-id: 94c528799e31b2ffb02cff675604e7cce639687f
