Update gitlab-styles from 4.3.0 to 6.1.0

What does this MR do?

Updates gitlab-styles from 4.3.0 to 6.1.0 mainly to update rubocop from 0.82.0 to 0.93.1 to specify TargetRubyVersion: 3.0.

.rubocop_todo.yml was updated by rubocop --auto-gen-config. Otherwise we would have 1045 additional offenses. There is no out-of-date todos: cf. master...rubocop-re-auto-gen-config-20200228

Follows up !4703 (merged)

Related issues

Replaces !4899 (closed)

Part of &5149 (closed)

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
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened