Clarify IPv6 readiness
Clarify that IPv6 is supported on hosted installations but not on GitLab.com.
Closes https://gitlab.com/gitlab-com/www-gitlab-com/issues/1672
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Clarify that IPv6 is supported on hosted installations but not on GitLab.com.
Closes https://gitlab.com/gitlab-com/www-gitlab-com/issues/1672