Remove unnamed namespace in headers (#43689)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/43689
Test Plan: Imported from OSS
Reviewed By: eellison, asuhan
Differential Revision: D23367636
Pulled By: bertmaher
fbshipit-source-id: ddb6d34d2f7cadff3a591c3650e1dd1b401c3d2d
