Planning: set use_ros_time default conf to false. (#1341)

* Planning: set use_ros_time default conf to false.

* Planning: relaxed the jerk continuity requirement for better robustness.

modules/planning/conf/planning.conf

 --flagfile=modules/common/data/global_flagfile.txt
 --adapter_config_path=modules/planning/conf/adapter.conf
---use_ros_time=true
+--nouse_ros_time

modules/planning/tasks/qp_spline_st_speed/qp_spline_st_graph.cc

@@ -163,7 +163,7 @@ Status QpSplineStGraph::ApplyConstraint(
   }
 
   // smoothness constraint
-  if (!constraint->AddThirdDerivativeSmoothConstraint()) {
+  if (!constraint->AddSecondDerivativeSmoothConstraint()) {
     const std::string msg = "add smoothness joint constraint failed!";
     AERROR << msg;
     return Status(ErrorCode::PLANNING_ERROR, msg);
@@ -226,7 +226,6 @@ Status QpSplineStGraph::ApplyConstraint(
 
   DCHECK_EQ(t_evaluated_.size(), accel_lower_bound.size());
   DCHECK_EQ(t_evaluated_.size(), accel_upper_bound.size());
-  // TODO: add accel constraint below
   if (!constraint->AddSecondDerivativeBoundary(t_evaluated_, accel_lower_bound,
                                                accel_upper_bound)) {
     const std::string msg = "Fail to apply acceleration constraints.";