Replace load_boston due to Ethical Issues

[koaning]

What does this PR do?

This replaces the load_boston dataset with load_diabetes. The load_boston dataset is up for removal from scikit-learn due to the ethical issues related to the variables in it. scikit-learn/scikit-learn#16155

Fixes # (issue)

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[codecov]

Codecov Report

Merging #629 (9155e78) into master (31f0f51) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #629   +/-   ##
=======================================
  Coverage   71.87%   71.87%           
=======================================
  Files         118      118           
  Lines        7146     7146           
=======================================
  Hits         5136     5136           
  Misses       2010     2010           

Flag	Coverage Δ
cpu	71.87% <100.00%> (ø)
pytest	71.87% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pl_bolts/models/regression/linear_regression.py	98.70% <100.00%> (ø)

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[akihironitta]

@koaning Hi, thank you for bringing this up and for providing the issue link.

[akihironitta]

There are a number of replacements suggested in the linked issue, but as @koaning suggests, load_diabetes would be a reasonable replacement because the dataset is small and is included already in scikit-learn.

[edgarriba]

LGTM. Thanks for bringing this up. We are good to go once the tests pass.

[akihironitta]

I believe the failing test is unrelated to the change in this PR. It's being fixed in #633. LGTM!

[akihironitta]

Let me check the failing tests

[akihironitta]

All the failing tests have been addressed in other PRs. LGTM!