refactor(behavior_velocity_occlusion_spot_module): remove unnecessary declaration

[veqcc]

Description

This fixes build-and-test-differential / clang-tidy-differential errors in #6987:

/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/debug.cpp:36:29: error: using decl 'createDefaultMarker' is unused [misc-unused-using-decls,-warnings-as-errors]
using tier4_autoware_utils::createDefaultMarker;
                            ^
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/debug.cpp:36:29: note: remove the using
using tier4_autoware_utils::createDefaultMarker;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~

/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:60:16: error: using decl 'ArcCoordinates' is unused [misc-unused-using-decls,-warnings-as-errors]
using lanelet::ArcCoordinates;
               ^
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:60:16: note: remove the using
using lanelet::ArcCoordinates;
~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:64:16: error: using decl 'ConstLineString2d' is unused [misc-unused-using-decls,-warnings-as-errors]
using lanelet::ConstLineString2d;
               ^
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:64:16: note: remove the using
using lanelet::ConstLineString2d;
~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:66:26: error: using decl 'fromArcCoordinates' is unused [misc-unused-using-decls,-warnings-as-errors]
using lanelet::geometry::fromArcCoordinates;
                         ^
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:66:26: note: remove the using
using lanelet::geometry::fromArcCoordinates;
~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:67:26: error: using decl 'toArcCoordinates' is unused [misc-unused-using-decls,-warnings-as-errors]
using lanelet::geometry::toArcCoordinates;
                         ^
/__w/autoware.universe/autoware.universe/planning/behavior_velocity_occlusion_spot_module/src/occlusion_spot_utils.hpp:67:26: note: remove the using
using lanelet::geometry::toArcCoordinates;
~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

Tests performed

No

Effects on system behavior

Interface changes

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[shmpwk]

LGTM