Remove compiler check for MSVC < 2015U3.
Remove compiler check for MSVC < 2015U3.

This was meant to be included by PR #5, but was accidentally
merged by #15. Since we need to update NVIDIA's internal CI to
use a newer MSVC, this change this must be removed for now.

NVlabs/CUB,NVIDIA/cub,NVlabs/cub