Switched CONTRIBUTING.md style guide recommendation for method chaining
As discussed on slack: https://gitlab.slack.com/archives/development/p1487871145007564 following new Rubocop check.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
As discussed on slack: https://gitlab.slack.com/archives/development/p1487871145007564 following new Rubocop check.