`matrix_client_schildichat_docker_image` was adjusted to use the
Github Container Registry in 171f5f84a2cd058f0c53780, but the Renovate marker was not adjusted.

Related to: https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3485

Related to 0241c71a4c

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3270#issuecomment-2143782962

With this change, it should be possible for people to adjust the Docker
dependency from `docker.service` to something else (e.g. `pkg-ContainerManager-dockerd.service`),
or to completely eliminate it by setting `devture_systemd_docker_base_docker_service_name` to an empty string.

This makes it easier for people to use the playbook against a Synology DSM server.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3333

Ref:
- https://github.com/matrix-org/matrix-react-sdk/pull/12153
- https://github.com/element-hq/element-web/pull/26885

Technically, it may still work for Schildichat, because it's stuck in
the past. It will catch up soon anyway.

Putting each client into its own network was good for isolation,
but it's quite wasteful in terms of the container network pool.