pytorch

dfc4be20 - Fix broken reference in sync bn doc (#38890)

Fix broken reference in sync bn doc (#38890) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/38890 Differential Revision: D21722162 Pulled By: ezyang fbshipit-source-id: a7d18239917b2886fe8c1c0aaf42fc8491c8e10c