Fix SimpleITK install on minimal tox run

[oesteban]

Summary

• pin SimpleITK to the 2.5 series so uv resolves a wheel instead of an old source build

Testing

• tox -e py312-latest --notest -v

---

https://chatgpt.com/codex/tasks/task_e_68811c802db08330bc1b15827676ff37

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.09%. Comparing base (5647caf) to head (85c2709).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #269   +/-   ##
=======================================
  Coverage   95.09%   95.09%           
=======================================
  Files          16       16           
  Lines        1979     1979           
  Branches      265      265           
=======================================
  Hits         1882     1882           
  Misses         77       77           
  Partials       20       20           

Flag	Coverage Δ
unittests	95.07% <ø> (ø)

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