chore(mpc): add default value

[TakaHoribe]

Description

Add default parameter value to fix the test in mpc

Tests performed

pass test on CI

Effects on system behavior

None

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Post-review checklist for the PR author

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After all checkboxes are checked, anyone who has write access can merge the PR.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.99 ⚠️

Comparison is base (7a0e1c0) 15.40% compared to head (13da41f) 14.41%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3976      +/-   ##
==========================================
- Coverage   15.40%   14.41%   -0.99%     
==========================================
  Files        1350     1456     +106     
  Lines       96065   102643    +6578     
  Branches    29732    29722      -10     
==========================================
- Hits        14796    14794       -2     
- Misses      65108    71689    +6581     
+ Partials    16161    16160       -1     

Flag	Coverage Δ		*Carryforward flag
differential	46.95% <ø> (?)
total	14.41% <ø> (-0.99%)	⬇️	Carriedforward from e1be8cc

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

Impacted Files	Coverage Δ
..._controller/include/mpc_lateral_controller/mpc.hpp	63.15% <ø> (ø)

... and 113 files with indirect coverage changes

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[TomohitoAndo]

LGTM