Fixes # .

Summary/Motivation:

This resolves two issues in the test harness:

• update the importer for linear-tree to mark it as "unavailable" if it is incompatible with scikit-learn (linear-tree <= 0.3.5 is incompatible with scikit-learn >= 1.7.0)
• skip test_nonconvexqp_locally_optimal in Xpress 9.8: we have not found a way to force Xpress to actually use a local solver in this release. A support request has been submitted upstream.

Changes proposed in this PR:

• Update linear-tree importer to verify dependency versions

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