Remove copy-pasted code in THCTensorTopK.cuh (#28995)
Summary:
This is independent from https://github.com/pytorch/pytorch/pull/28989, but when https://github.com/pytorch/pytorch/issues/28989 get landed, this fixes https://github.com/pytorch/pytorch/issues/28792 .
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28995
Differential Revision: D18265797
Pulled By: soumith
fbshipit-source-id: 6dd7cffd05aa65e4b366f1c40b8bda0a633e3154
