Upgrading Mattermost configuration for Gitlab 11
Upgrade the mattermost configuration option according with the new options in Gitlab 11 https://docs.gitlab.com/omnibus/gitlab-mattermost/#upgrading-gitlab-mattermost-from-versions-prior-to-11-0
Upgrade the mattermost configuration option according with the new options in Gitlab 11 https://docs.gitlab.com/omnibus/gitlab-mattermost/#upgrading-gitlab-mattermost-from-versions-prior-to-11-0