refactor(behavior_velocity_occlusion_spot_module): remove unnecessary declaration

Signed-off-by: Ryuta Kambe <ryuta.kambe@tier4.jp>

Author: veqcc

planning/behavior_velocity_occlusion_spot_module/src/debug.cpp

@@ -33,7 +33,6 @@ using BasicPolygons = std::vector<lanelet::BasicPolygon2d>;
 using occlusion_spot_utils::PossibleCollisionInfo;
 using tier4_autoware_utils::appendMarkerArray;
 using tier4_autoware_utils::calcOffsetPose;
-using tier4_autoware_utils::createDefaultMarker;
 using tier4_autoware_utils::createMarkerColor;
 using tier4_autoware_utils::createMarkerOrientation;
 using tier4_autoware_utils::createMarkerPosition;