Revert D25717510: Clean up some type annotations in benchmarks/fastrnns
Test Plan: revert-hammer
Differential Revision:
D25717510 (https://github.com/pytorch/pytorch/commit/7d0eecc666645f7ad83e7acec7b240ee7860ac92)
Original commit changeset: 4f6431d140e3
fbshipit-source-id: 2bcc19cd434047f3857e0d7e804d34f72e566c30
