Fix invalid device_accessible namespace (#6269)

Author: davebayer

cudax/test/execution/test_stream_context.cu

@@ -135,7 +135,7 @@ void bulk_on_stream_scheduler()
 
   using _env_t = cudax::env_t<cuda::mr::device_accessible>;
   auto mr      = cudax::device_memory_resource{_dev};
-  auto mr2     = cudax::any_resource<cudax::device_accessible>(mr);
+  auto mr2     = cudax::any_resource<cuda::mr::device_accessible>(mr);
   _env_t env{mr, cuda::get_stream(sch), ex::par_unseq};
   auto buf = cudax::make_async_buffer<int>(sctx, mr2, 10, 40, env); // a device buffer of 10 integers, initialized to 40
   cuda::std::span data{buf};