Moved GitLab Basics link
As requested in https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/793, I moved the link to the General Onboarding.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
As requested in https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/793, I moved the link to the General Onboarding.