Fix typo

Allocation is for device USM, not shared USM.

adoc/code/usm_device.cpp

@@ -9,7 +9,7 @@ int main() {
   // Create a default queue to enqueue work to the default device
   queue myQueue;
 
-  // Allocate shared memory bound to the device and context associated to the
+  // Allocate device memory bound to the device and context associated to the
   // queue
   int* data = sycl::malloc_device<int>(1024, myQueue);