BLD: Pin eigen3

[mferrera]

Resolves #1488

Eigen3 v5.0.0 was released on vcpkg. This pins the version for the Windows build.

Checklist

• Tests added (if not, comment why)
• Test coverage equal or up from main (run pytest with --cov=src/ --cov-report term-missing)
• If not squash merging, every commit passes tests
• Appropriate commit prefix and precise commit message used
• All debug prints and unnecessary comments removed
• Docstrings are correct and updated
• Documentation is updated, if necessary
• Latest main rebased/merged into branch
• Added comments on this PR where appropriate to help reviewers
• Moved issue status on project board
• Checked the boxes in this checklist ✅

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.65%. Comparing base (0375fed) to head (bb18153).
⚠️ Report is 159 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1489      +/-   ##
==========================================
- Coverage   80.02%   79.65%   -0.38%     
==========================================
  Files          98      103       +5     
  Lines       13680    14389     +709     
  Branches     2203     2246      +43     
==========================================
+ Hits        10948    11461     +513     
- Misses       1999     2196     +197     
+ Partials      733      732       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.