[Mercure] Fix docker compose healthcheck command

[humblots]

Hello 👋

The mercure-bundle recipe doesn't include the latest healthcheck test available in the nercure documentation in the compose.yaml for an implementation behind Traefik.

mercure:
  # [...]
  healthcheck:
    test: ["CMD", "curl", "-f", "https://localhost/healthz"]
    timeout: 5s
    retries: 5
    start_period: 60s

Instead of :

mercure:
  # [...]
  healthcheck:
    test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost/healthz"]
    timeout: 5s
    retries: 5
    start_period: 60s

The latest image doesn't come with curl which cause the container to never be healthy and nor routed by traefik. Updating the test command fixes the issue.