Documentation: Docstring examples for SKLearnClassifier and SKLearnRegressor do not work

[timovdk]

The examples in the docstrings for SKLearnClassifier and SKLearnRegressor are currently not working. This is because of several small issues:

• General issues:
  • Importing layers from keras.src.layers instead of keras.layers
  • Importing Model from keras.src.layers instead of keras.models
  • Unnecessary usage of [] around the output layer
• SKLearnClassifier docstring issue:
  • The example uses n_classes=3, but this leads to a scikit-learn error: ValueError: n_classes(3) * n_clusters_per_class(2) must be smaller or equal 2**n_informative(2)=4
• SKLearnRegressor docstring issue:
  • Uses softmax activation where linear would be more appropriate (regression problem that does not fall between [0, 1]), causing warnings.

I will open a PR to address these issues shortly.