FIX Remove spurious IsolationForest arguments

[betatim]

These arguments should not have been added, now they are gone. This removes the warm_start constructor argument that was unsupported and only ever raised. The same goes for the sample_weights argument used in fit() and friends.

No deprecation cycles because this fixes a bug (arguments should never have been there in the first place).

Towards #8420

[coderabbitai]

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• python/cuml/tests/test_isolation_forest.py

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• python/cuml/tests/test_isolation_forest.py

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Updated Isolation Forest APIs to remove unsupported warm_start and sample_weight options.
  • Simplified fit and fit_predict usage by removing unsupported sample-weight arguments.
  • Updated documentation and compatibility checks to reflect the supported functionality.

Walkthrough

IsolationForest no longer exposes warm_start or sample_weight. Its constructor, fitting methods, documentation, and parameter mappings were updated. Obsolete rejection tests and sample-weight compatibility XFAILs were removed.

Changes

IsolationForest interface cleanup

Layer / File(s)	Summary
Remove unsupported estimator interfaces python/cuml/cuml/ensemble/isolation_forest.pyx	Removes warm_start from estimator configuration and removes sample_weight from fit and fit_predict.
Update unsupported-option tests python/cuml/tests/test_isolation_forest.py, python/cuml/tests/test_sklearn_compatibility.py	Removes tests for unsupported direct-fitting arguments and sample-weight compatibility XFAILs.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 7b9ba

This PR removes unsupported IsolationForest arguments and updates the related tests; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the removal of unsupported IsolationForest arguments and links the change to issue #8420.
Title check	✅ Passed	The title clearly and concisely describes the removal of unsupported IsolationForest arguments.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[jcrist]

Thanks! I've moved this to a breaking change just to note the arg removal (though I doubt anyone is relying on unsupported args from a just released estimator).

One small comment, do with it what you will.

[betatim]

Thanks for the breaking label, it is the smarter choice.

[betatim]

/merge