Update custom cop rule as per updating RuboCop to v1

What does this MR do?

Updates a custom cop rule as per updating RuboCop to v1 (!6355 (merged)). Upgrading guide to v1 is available at https://docs.rubocop.org/rubocop/v1_upgrade_notes.html

Related issues

Follows up !6355 (merged)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• [n/a] Documentation created/updated
• [n/a] Tests added
• [n/a] Integration tests added to GitLab QA
• [n/a] Equivalent MR/issue for the GitLab Chart opened