feat(tier4_planning_rviz_plugin): remove z offset from the bound

[purewater0901]

Description

Remove z offset from the left and right bound to clean the visualization.

Tests performed

Not applicable.

Effects on system behavior

Not applicable.

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[yukkysaito]

LGTM

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.02 🎉

Comparison is base (2c3a860) 14.08% compared to head (a2be88a) 14.10%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3551      +/-   ##
==========================================
+ Coverage   14.08%   14.10%   +0.02%     
==========================================
  Files        1399     1399              
  Lines       97918    97735     -183     
  Branches    29058    28953     -105     
==========================================
  Hits        13788    13788              
+ Misses      69459    69278     -181     
+ Partials    14671    14669       -2     

Flag	Coverage Δ		*Carryforward flag
differential	0.00% <ø> (?)
total	14.10% <ø> (+0.02%)	⬆️	Carriedforward from 2c3a860

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
...ier4_planning_rviz_plugin/include/path/display.hpp	0.00% <ø> (ø)
...ner/include/behavior_path_planner/data_manager.hpp	50.00% <ø> (ø)
.../include/behavior_path_planner/planner_manager.hpp	0.00% <ø> (ø)
...th_planner/scene_module/scene_module_interface.hpp	34.92% <ø> (ø)
...nner/scene_module/side_shift/side_shift_module.hpp	100.00% <ø> (ø)
...de/behavior_path_planner/utils/avoidance/utils.hpp	∅ <ø> (∅)
...nner/include/behavior_path_planner/utils/utils.hpp	100.00% <ø> (ø)
...or_path_planner/src/behavior_path_planner_node.cpp	19.73% <ø> (+0.02%)	⬆️
...er/src/scene_module/avoidance/avoidance_module.cpp	3.43% <ø> (+0.01%)	⬆️
...lanner/src/scene_module/avoidance_by_lc/module.cpp	0.00% <ø> (ø)
... and 10 more

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