Support the latest scikit-learn

[jeongyoonlee]

Is your feature request related to a problem? Please describe.

Current causal tree implementation depends on scikit-learn<=1.0.2, and it raises Cython errors with the latest scikit-learn due to the change introduced in scikit-learn/scikit-learn#22328.

Describe the solution you'd like

Updating the caudal tree code with the changes in scikit-learn/scikit-learn#22328.

Describe alternatives you've considered

Adding scikit-learn/scikit-learn/tree as a subtree (ref). This may help better sync the causalml and scikit-learn's tree implementations while allowing the usage of the latest scikit-learn.

Additional context
N/A

[ras44]

see also discussion in #619

[jeongyoonlee]

Resolved with #686