Fixes # .

Summary/Motivation:

This sets an upper limit on the scikit-learn version to work around testing failures in contrib.piecewise stemming from the unmaintained linear-tree package. @emma58 is working on a better solution that will replace the linear-tree dependency with something that is being maintained. This PR is a temporary fix until then.

Upon opening this PR we also discovered a new testing issue with cpython 3.13.4. This new Python version introduces a slight change in the formatting of some logging messages which we've tracked to this resolved issue: python/cpython#91555. We need feedback from @jsiirola on how to proceed.

Changes proposed in this PR:

• Temporarily bound scikit-learn version
• Temporarily pin Python 3.13 version used for testing

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