Fix the link to the "Announce a deployment" doc, now in the takeoff project
This addresses https://gitlab.com/gitlab-com/infrastructure/issues/1361 and depends on https://gitlab.com/gitlab-org/takeoff/merge_requests/7.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
This addresses https://gitlab.com/gitlab-com/infrastructure/issues/1361 and depends on https://gitlab.com/gitlab-org/takeoff/merge_requests/7.