refactor(behavior_path_planner): remove unnecessary parameters (autowarefoundation#1172)

Signed-off-by: Takayuki Murooka <takayuki5168@gmail.com>

Author: takayuki5168

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

@@ -24,5 +24,3 @@
     enable_cog_on_centerline: false
     input_path_interval: 2.0
     output_path_interval: 2.0
-
-    visualize_maximum_drivable_area: true