Fix an unchaged filtering extent in PerssonTci

[yoonso0-0]

Proposed changes

A quick fix to a severe bug in #5779

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Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
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Further comments

[yoonso0-0]

@knelli2 @nilsdeppe I pushed a fix for the test together. Basically adding one more test case that the second highest mode is excited but TCI only monitors the highest mode. This test would have flagged error for the previous mistake (keep using 1 not num_higest_modes in PerssonTci.cpp).