Fix a typo in EmbeddingBag.cu (#42742)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/42742
Reviewed By: smessmer
Differential Revision: D23011029
Pulled By: mrshenli
fbshipit-source-id: 615f8b876ef1881660af71b6e145fb4ca97d2ebb
