fix sigma in the middle of when word (#16227)
Summary:
there is a random sigma in the when word on :
https://pytorch.org/cppdocs/contributing.html
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16227
Differential Revision: D13762753
Pulled By: goldsborough
fbshipit-source-id: 3d4bf4be859a3069402fe8c3fbc8ebee4f25cc5a
