fix(avoidance): change return dead line param (#814)

Signed-off-by: satoshi-ota <satoshi.ota928@gmail.com>

Author: satoshi-ota

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

@@ -219,7 +219,7 @@
         return_dead_line:
           goal:
             enable: true                                # [-]
-            buffer: 30.0                                # [m]
+            buffer: 3.0                                 # [m]
           traffic_light:
             enable: true                                # [-]
             buffer: 3.0                                 # [m]