Fix regression on default value for find_unused_parameters

[awaelchli]

What does this PR do?

Fixes #14089

The change was unintentionally introduced in #13405, #13744. Tests have been added that fail on master.

Does your PR introduce any breaking changes? If yes, please list them.

No

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I made sure I had fun coding 🙃

cc @Borda @tchaton @rohitgr7 @justusschock @kaushikb11 @awaelchli @akihironitta

[carmocca]

@awaelchli This was merged with Windows job failures. Can you fix them?

[awaelchli]

Yes, I didn't notice.
The logic is correct. The test just needs to be skipped on Windows.