remove useless box_tmp (#936)

oneflow/core/graph/task_graph.cpp

@@ -54,7 +54,6 @@ TaskGraph::TaskGraph(std::unique_ptr<const LogicalGraph>&& logical_gph) {
   void TaskGraph::method_name BLD_SUB_TSK_GPH_MTHD_ARGS()
 
 DEFINE_BLD_SUB_TASK_GRAPH_METHOD(BldSubTskGphByBoxing) {
-  std::vector<TaskNode*> sorted_out_box_tmp;
   std::vector<TaskNode*>* sorted_out_box = nullptr;
   if (logical2sorted_out_box->find(src_logical) == logical2sorted_out_box->end()) {
     BuildOutBoxing(src_logical, sorted_src_comp_tasks, &((*logical2sorted_out_box)[src_logical]),
@@ -62,7 +61,6 @@ DEFINE_BLD_SUB_TASK_GRAPH_METHOD(BldSubTskGphByBoxing) {
   }
   sorted_out_box = &(logical2sorted_out_box->at(src_logical));
 
-  std::vector<TaskNode*> sorted_in_box_tmp;
   std::vector<TaskNode*>* sorted_in_box = nullptr;
   if (logical2sorted_in_box->find(dst_logical) == logical2sorted_in_box->end()) {
     BuildInBoxing(dst_logical, sorted_dst_comp_tasks, &((*logical2sorted_in_box)[dst_logical]),