CUDA Docs: Improve forall docstring
CUDA Docs: Improve forall docstring

stuartarchibald/numba,stonebig/numba,stuartarchibald/numba,IntelLabs/numba,stuartarchibald/numba,seibert/numba,stonebig/numba,gmarkall/numba,numba/numba,stonebig/numba,sklam/numba,sklam/numba,seibert/numba,cpcloud/numba,stuartarchibald/numba,sklam/numba,cpcloud/numba,IntelLabs/numba,stonebig/numba,sklam/numba,cpcloud/numba,numba/numba,cpcloud/numba,stonebig/numba,numba/numba,numba/numba,IntelLabs/numba,gmarkall/numba,sklam/numba,cpcloud/numba,seibert/numba,seibert/numba,gmarkall/numba,seibert/numba,gmarkall/numba,numba/numba,stuartarchibald/numba,IntelLabs/numba,gmarkall/numba,IntelLabs/numba