Detail the use of Tag Locker in Zendesk
Replaces https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/3847
Fixes gitlab-com/support#273
\cc @MrChrisW
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Replaces https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/3847
Fixes gitlab-com/support#273
\cc @MrChrisW