fix(autoware_launch): remove use_pointcloud_container flag completely (autowarefoundation#864)

Author: kminoda

autoware_launch/launch/autoware.launch.xml

@@ -4,7 +4,6 @@
   <arg name="map_path" description="point cloud and lanelet2 map directory path"/>
   <arg name="vehicle_model" default="sample_vehicle" description="vehicle model name"/>
   <arg name="sensor_model" default="sample_sensor_kit" description="sensor model name"/>
-  <arg name="use_pointcloud_container" default="true" description="launch pointcloud container"/>
   <arg name="pointcloud_container_name" default="pointcloud_container"/>
   <arg name="data_path" default="$(env HOME)/autoware_data" description="packages data and artifacts directory path"/>