Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2427
`metrics_enabled` should only expose the metrics locally, on the
container network, so that a local Prometheus can consume them.
Exposing them publicly should be done via a separate toggle (`metrics_proxying_enabled`).
This is how all other roles work, so this makes these mautrix roles consistent with the rest.
