fix(planning): reduce longitudinal velocity delta time

Signed-off-by: Muhammad Zulfaqar Azmi <zulfaqar.azmi@tier4.jp>

Author: zulfaqar-azmi-t4

autoware_launch/config/planning/scenario_planning/lane_driving/behavior_planning/behavior_path_planner/lane_change/lane_change.param.yaml

@@ -53,7 +53,7 @@
           rear_vehicle_safety_time_margin: 1.0
           lateral_distance_max_threshold: 2.0
           longitudinal_distance_min_threshold: 3.0
-          longitudinal_velocity_delta_time: 0.8
+          longitudinal_velocity_delta_time: 0.6
 
         # lane expansion for object filtering
         lane_expansion: