A tiny fix in MT19937RNGEngine (#63219)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63219
Reviewed By: VitalyFedyunin
Differential Revision: D30341484
Pulled By: ezyang
fbshipit-source-id: 0ff4499d0f4a3dfeb991c0f10fe3248c6ca1c992
