Remove the pygam dependency and allow latest versions of Cython, numpy, scipy, scikit-learn

[jeongyoonlee]

Proposed changes

This PR fixes #796 by removing pygam from pyproject.toml. It also removes the upper version restrictions for Cython, numpy, scipy and scikit-learn.

• resolves #796 remove dep on pygam, use IsotonicRegression #803 replaced pygam with the Isotonic calibration in scikit-learn and allowed to use the latest scipy, Cython, and numpy.
• The recent xgboost==2.1.4 release resolved the compatibility issue with scikit-learn==1.6 in Adapt to scikit-learn 1.6 estimator tag changes dmlc/xgboost#11021 and allowed to use the latest scikit-learn.
• The noexcept modifier has been added to the Cython code to comply with Cython 3.x (ref)

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