feat(tests): Add test for bad withdrawals root

[pdobacz]

🗒️ Description

One more test for header validation coverage, this time specific to withdrawals, so added to Shanghai tests.

🔗 Related Issues or PRs

N/A.

✅ Checklist

• All: Ran fast tox checks to avoid unnecessary CI fails, see also Code Standards and Enabling Pre-commit Checks:

  uvx tox -e static

• All: PR title adheres to the repo standard - it will be used as the squash commit message and should start type(scope):.
• All: Considered adding an entry to CHANGELOG.md.
• All: Set appropriate labels for the changes (only maintainers can apply labels).

[marioevz]

LGTM, thanks!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.08%. Comparing base (fa1a2bb) to head (5734e73).
⚠️ Report is 16 commits behind head on forks/osaka.

Additional details and impacted files

@@               Coverage Diff               @@
##           forks/osaka    #1746      +/-   ##
===============================================
- Coverage        86.08%   86.08%   -0.01%     
===============================================
  Files              743      743              
  Lines            44072    44076       +4     
  Branches          3891     3891              
===============================================
+ Hits             37938    37941       +3     
- Misses            5656     5657       +1     
  Partials           478      478              

Flag	Coverage Δ
unittests	86.08% <ø> (-0.01%)	⬇️

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