Remove erroneous trailing backslashes (#43318)
Summary:
They were likely copied from some macro definition, but they do not
belong to macro definitions here.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43318
Reviewed By: pbelevich
Differential Revision: D23241526
Pulled By: mrshenli
fbshipit-source-id: e0b5eddfde2c882bb67f56d84ee79281cc5fc941
