Rubocop: Address let! usage in tests

[colinbruce]

What

Remove RSpec/LetSetup from rubocop_todo
Remove all superfluous let! invocations from the RSpec code

Checklist

Before you ask people to review this PR:

• Tests and rubocop should be passing: bundle exec rake
• Github should not be reporting conflicts; you should have recently run git rebase main.
• There should be no unnecessary whitespace changes. These make diffs harder to read and conflicts more likely.
• The PR description should say what you changed and why, with a link to the JIRA story.
• You should have looked at the diff against main and ensured that nothing unexpected is included in your changes.
• You should have checked that the commit messages say why the change was made.

[jsugarman]

👍 just one commented out let ripe for removal

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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