Add duplicate dust test vector for zero fee channels

[carlaKC]

New test vector added to the spec.

Interop is complete so this closes #3789.

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[TheBlueMatt]

Thanks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.33%. Comparing base (21110c8) to head (1994661).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4229      +/-   ##
==========================================
- Coverage   89.33%   89.33%   -0.01%     
==========================================
  Files         180      180              
  Lines      138353   138481     +128     
  Branches   138353   138481     +128     
==========================================
+ Hits       123598   123712     +114     
- Misses      12132    12146      +14     
  Partials     2623     2623              

Flag	Coverage Δ
fuzzing	35.97% <ø> (+0.06%)	⬆️
tests	88.69% <ø> (-0.01%)	⬇️

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