Automatically enable new RuboCop cops

What does this MR do and why?

For housekeeping:

• Automatically enable new cops, per: https://docs.rubocop.org/rubocop/versioning.html#enablingdisabling-pending-cops-in-bulk.
• Fix some of the simpler violations in the project.

We should eventually turn RuboCop on as a breaking check, but first we need to continue to clean up a bit.

@sarahgerman Do you have: https://docs.rubocop.org/rubocop/integration_with_other_tools.html#visual-studio-code set up? That should allow you to catch things in files you're working in.

Merge request acceptance checklist

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• I have evaluated the MR acceptance checklist for this merge request.