fix mac compile error

paddle/fluid/operators/parallel_do_op.cc

@@ -163,8 +163,7 @@ class ParallelDoOp : public framework::OperatorBase {
       auto &place = places[place_idx];
       auto *cur_scope = sub_scopes[place_idx];
 
-      workers.emplace_back(
-          framework::Async([program, cur_scope, place, block, place_idx] {
+      workers.emplace_back(framework::Async([program, cur_scope, place, block] {
         framework::Executor executor(place);
         executor.Run(*program, cur_scope, block->ID(),
                      false /*create_local_scope*/);
@@ -239,8 +238,7 @@ class ParallelDoGradOp : public framework::OperatorBase {
       auto *cur_scope = sub_scopes[i];
 
       // execute
-      workers.emplace_back(
-          framework::Async([program, cur_scope, place, block, i] {
+      workers.emplace_back(framework::Async([program, cur_scope, place, block] {
         framework::Executor executor(place);
         executor.Run(*program, cur_scope, block->ID(),
                      false /*create_local_scope*/);