Update doc to remove unicorn service file if using existing nginx/passenger
Related to https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1764#note_19486326
If unicorn is disabled, its service file should be removed.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Related to https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1764#note_19486326
If unicorn is disabled, its service file should be removed.