doc: update for the new scheduler component API

doc/doxygen/chapters/350_modularized_scheduler.doxy

@@ -229,7 +229,7 @@ static void initialize_eager_prefetching_center_policy(unsigned sched_ctx_id)
     /* Each Worker Component has a Flow-control Fifo Component as
      * father */
     struct starpu_sched_component * worker_component =
-	  starpu_sched_component_worker_get(i);
+	  starpu_sched_component_worker_new(i);
     struct starpu_sched_component * fifo_component =
 	  starpu_sched_component_fifo_create(&fifo_data);
     fifo_component->add_child