Deletes unused line in test_autocast_rnn (#73195)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/73195
Reviewed By: mruberry
Differential Revision: D34557677
Pulled By: ngimel
fbshipit-source-id: 284018b4596471332d0e90a08e2c38303fb2b3ae
(cherry picked from commit bbf6913009e206c02e124c49ab80ef9596f7fcad)
