Fixes #1253 Build sklearn pipeline tests for CVScores

[lwgray]

Build Sklearn Pipeline Tests for the following visualizers

• [x] - CVScores

• [x] Is the commit message formatted correctly?
• [ ] Have you noted the new functionality/bugfix in the release notes of the next release?

• [ ] Included a sample plot to visually illustrate your changes?
• [x] Do all of your functions and methods have docstrings?
• [x] Have you added/updated unit tests where appropriate?
• [x] Have you updated the baseline images if necessary?
• [x] Have you run the unit tests using pytest?
• [x] Is your code style correct (are you using PEP8, pyflakes)?
• [ ] Have you documented your new feature/functionality in the docs?

• [ ] Have you built the docs using make html?

[codecov[bot]]

Codecov Report

Merging #1254 (a636a04) into develop (b9626fc) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #1254   +/-   ##
========================================
  Coverage    90.61%   90.61%           
========================================
  Files           92       92           
  Lines         5213     5213           
========================================
  Hits          4724     4724           
  Misses         489      489           

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