[CUDA] Bump the latest supported CUDA version to 11.4.

This should reduce the amount of noise issued by clang for the recent-ish CUDA
versions.

Clang still does not support all the features offered by NVCC, but is expected
to handle CUDA headers and produce binaries for all GPUs supported by NVCC.

Differential Revision: https://reviews.llvm.org/D108248