refactor(speed_bump): use getOrDeclareParameter

[TakaHoribe]

Description

use tier4_autoware_utils::getOrDeclareParameter for the ros parameter to prevent duplicate parameter declaration.

Tests performed

Run psim

Effects on system behavior

None

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[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (7f5f946) 15.11% compared to head (91a3019) 15.11%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4773   +/-   ##
=======================================
  Coverage   15.11%   15.11%           
=======================================
  Files        1568     1568           
  Lines      108141   108141           
  Branches    33184    33184           
=======================================
  Hits        16347    16347           
  Misses      73999    73999           
  Partials    17795    17795           

Flag	Coverage Δ		*Carryforward flag
differential	19.23% <0.00%> (?)
total	15.11% <ø> (+<0.01%)	⬆️	Carriedforward from 7f5f946

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

Files Changed	Coverage Δ
...ehavior_velocity_speed_bump_module/src/manager.cpp	0.00% <0.00%> (ø)

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