Update Dependencies for Latest Version Tests

[bbengfort]

This PR is an update to all of the test dependencies to ensure Yellowbrick works with the latest versions of it's primary dependencies.

This PR fixes #1327

I have made the following changes:

1. Updated the tests/requirements.txt
2. Updated all of the baseline images with the new versions
3. Fixed import errors and other issues in the code
4. Updated tests as necessary

CHECKLIST

• 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?
• Do all of your functions and methods have docstrings?
• Have you added/updated unit tests where appropriate?
• Have you updated the baseline images if necessary?
• Have you run the unit tests using pytest?
• 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 (must be run from docs/)?

[rebeccabilbro]

Godspeed on the dependency updates @bbengfort -- I know this stuff can be finicky. Let me know if you would like me to pre-approve to help make merging smoother once CI passes. Really appreciate you diving back in to help revive Yellowbrick and get it back in sync with the latest scikit-learn!