matrix: Update synapse to 0.18.0

roles/matrix/defaults/main.yml

roles/matrix/files/synapse-worker@.service

roles/matrix/files/synapse.service

roles/matrix/files/worker-appservice.yaml

roles/matrix/files/worker-federation_reader.yaml

roles/matrix/files/worker-federation_sender.yaml

roles/matrix/files/worker-media_repository.yaml

roles/matrix/tasks/main.yml

roles/matrix/templates/homeserver.yaml.j2

roles/matrix/templates/nginx.d.conf.j2