cleans up examples

[edublancas]

Describe your changes

Issue ticket number and link

Closes #270

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I have added thorough tests (when necessary).
• [x] I have added the right documentation in the docstring and changelog (when needed)

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:books: Documentation preview :books:: https://sklearn-evaluation--272.org.readthedocs.build/en/272/

[coveralls]

Pull Request Test Coverage Report for Build 4104359367

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.045%

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Totals
Change from base Build 4087696289:	0.0%
Covered Lines:	2969
Relevant Lines:	3157

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💛 - Coveralls