Remove FindCUDAToolkit backport (#645)

In 3f66927, `FindCUDAToolkit.cmake` was backported from CMake 3.31 to get
https://gitlab.kitware.com/cmake/cmake/-/commit/b38a8e77cb3c8401b3022a68f07a4fd77b290524, which was introduced in CMake 3.28. Since we now require CMake 3.30, we no longer need the backport.

Authors:
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #645