[BUG] Advice for installing CUDA toolkit in error message is wrong

[gmarkall]

Describe the bug
When the CUDA toolkit cannot be found, numba-cuda reports:

NvvmSupportError: libNVVM cannot be found. Do `conda install cudatoolkit`:
Could not find module 'nvvm.dll' (or one of its dependencies). Try using the full path with constructor syntax.

Steps/Code to reproduce bug

Attempt to compile a CUDA kernel when the CUDA toolkit is not installed.

Expected behavior

Instead of recommending cudatoolkit, it should recommend installation of packages as described in the current documentation:

https://nvidia.github.io/numba-cuda/user/overview.html#software