test(behavior velocity): fix unstable gtest

[taikitanaka3]

Related Issue(required)

#272

Description(required)

usually test passes with 100% CPU stress but it's success not in daily Test

• remove ubstable performance test
• make a test lighter

Review Procedure(required)

see test pass in CI

100% tests passed, 0 tests failed out of 6

Label Time Summary:
copyright     =   7.61 sec*proc (1 test)
cppcheck      =   0.54 sec*proc (1 test)
gtest         =   0.58 sec*proc (2 tests)
lint_cmake    =   0.30 sec*proc (1 test)
linter        =   9.17 sec*proc (4 tests)
xmllint       =   0.72 sec*proc (1 test)

Total Test time (real) =   9.76 sec
Finished <<< behavior_velocity_planner [10.0s]

Related PR(optional)

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