Boston dataset no longer avaliable in sklearn for classifier-decision-boundaries.ipynb and classifier-boundary-animations.ipynb

[mepland]

ImportError: 
`load_boston` has been removed from scikit-learn since version 1.2.

The Boston housing prices dataset has an ethical problem: as
investigated in [1], the authors of this dataset engineered a
non-invertible variable "B" assuming that racial self-segregation had a
positive impact on house prices [2]. Furthermore the goal of the
research that led to the creation of this dataset was to study the
impact of air quality but it did not give adequate demonstration of the
validity of this assumption.

The scikit-learn maintainers therefore strongly discourage the use of
this dataset unless the purpose of the code is to study and educate
about ethical issues in data science and machine learning.

[parrt]

I'd say we download and save as csv or find similar set like CA housing.

[mepland]

I think it should be switched to a new toy dataset, like CA housing.

[parrt]

Fixed by f86c5e1 (will appear after we merge back into master).