dev-cmd/style: Properly clean up the --display-cop-names option

[issyl0]

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• I remember making these changes as part of the RuboCop bump Dependabot PR (build(deps): bump rubocop from 1.48.1 to 1.49.0 in /Library/Homebrew #15136), but I must have not actually pushed them. Odd.

[MikeMcQuaid]

Thanks again @issyl0!