Draft: Bump gitlab-styles to v13

What does this MR do and why?

In order to keep our coding conventions within gitlab-qa consistent with the rest of the gitlab codebase we should ensure we keep the rubocop rules in alignment.

This MR bumps the gitlab-style gem to the latest version and fixes all newly detected rubocop warnings that are come with the updated version

Closes Bump gitlab-styles to v13 (#733)

How to set up and validate locally

bundle install
bundle exec rubocop

MR acceptance checklist

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• Commits include Changelog: trailer
• I have evaluated the MR acceptance checklist for this MR.