Fix testcase for invalid value at node initialization (backport #615)

[mergify]

Since PickNikRobotics/generate_parameter_library#339 the behavior of generate_parameter_library changed.
The parameter in the testcase can't even be declared as zero now (earlier it was declared with 0 but the validator failed later).

2026-05-18T07:35:36.9553861Z     [ RUN      ] FilterTest.TestLowPassWrenchFilterInvalidThenFixedParameter
2026-05-18T07:35:36.9555026Z     [ERROR] [1779089735.022610158] [TestLowPassWrenchFilterInvalidThenFixedParameter.TestLowPassFilter]: LowPass filter cannot be configured: parameter 'sampling_frequency' could not be set: Parameter {sampling_frequency} doesn't comply with floating point range. (type : N6rclcpp10exceptions30InvalidParameterValueExceptionE)
2026-05-18T07:35:36.9556068Z     unknown file: Failure
2026-05-18T07:35:36.9556522Z     C++ exception with description "parameter 'sampling_frequency' cannot be set because it was not declared" thrown in the test body.
2026-05-18T07:35:36.9556934Z     
2026-05-18T07:35:36.9557232Z     [  FAILED  ] FilterTest.TestLowPassWrenchFilterInvalidThenFixedParameter (7 ms)

Is this user-facing behavior change?

no

Did you use Generative AI?

no

---

This is an automatic backport of pull request #615 done by Mergify.

[mergify]

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Changes to be committed:
	modified:   test/control_filters/test_low_pass_filter_parameters.yaml

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   control_toolbox/test/control_filters/test_low_pass_filter.cpp

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.40%. Comparing base (7d4245e) to head (033b3ba).

Files with missing lines	Patch %	Lines
test/control_filters/test_low_pass_filter.cpp	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           humble     #630      +/-   ##
==========================================
- Coverage   59.46%   59.40%   -0.06%     
==========================================
  Files          28       28              
  Lines        1453     1451       -2     
  Branches      807      803       -4     
==========================================
- Hits          864      862       -2     
  Misses        233      233              
  Partials      356      356              

Flag	Coverage Δ
unittests	59.40% <50.00%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
test/control_filters/test_low_pass_filter.cpp	61.84% <50.00%> (-0.98%)	⬇️

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