CUDA: directly include cuda/iterator (llama/22936)

Before, we relied on a transient import from `cub/cub.cuh`, which is
bad practice to do as cub may not always expose cuda/iterator

ggml/src/ggml-cuda/argsort.cu

@@ -4,6 +4,7 @@
 #    include <cub/cub.cuh>
 #    if (CCCL_MAJOR_VERSION >= 3 && CCCL_MINOR_VERSION >= 1)
 #        define STRIDED_ITERATOR_AVAILABLE
+#        include <cuda/iterator>
 #    endif
 using namespace cub;
 #endif  // GGML_CUDA_USE_CUB