message: docs: update metrics example
  Fedora CoreOS replaced `nmap-ncat` with `socat`, so this updates the
  shell example to be directly usable there.
  Ref:
diff: @@ -16,7 +16,7 @@ To gather metrics from a locally running Zincati instance, it is sufficient to c
  For example, manual inspection can be performed via `ncat`:
  ```
  -$ sudo ncat -U --recv-only /run/zincati/private/metrics.promsock
  +$ sudo socat - UNIX-CONNECT:/run/zincati/private/metrics.promsock
  # HELP zincati_update_agent_last_refresh_timestamp UTC timestamp of update-agent last refresh tick.
  # TYPE zincati_update_agent_last_refresh_timestamp gauge
  