gcc-plugin: vector_scal example: unregister the handle, since it is not automatically done.

gcc-plugin/examples/vector_scal/vector_scal.c

@@ -184,6 +184,8 @@ main (void)
 
 #pragma starpu wait
 
+#pragma starpu unregister vector
+
     valid = check (NX, vector, FACTOR);
 
   } /* VECTOR is automatically freed here.  */