message: docs/metrics: fix links and minor errors
diff: Zincati tracks and exposes some of its internal metrics, in order to ease monitoring tasks across a large fleet of nodes.
  -Metrics are collected and exported according to [Prometheus] [textual format](prom-text), over a local endpoint.
  +Metrics are collected and exported according to [Prometheus] [textual format][prom-text], over a local endpoint.
  [Prometheus]: https://prometheus.io/
  [prom-text]: https://prometheus.io/docs/instrumenting/exposition_formats/
  @@ -11,7 +11,7 @@ Metrics are collected and exported according to [Prometheus] [textual format](pr
  To gather metrics from a locally running Zincati instance, it is sufficient to connect and read from the Unix-domain socket located at `/run/zincati/public/metrics.promsock`.
  -For example, manual inspection can be performed via `ncat`:
  +For example, manual inspection can be performed via `socat`:
  ```
  $ sudo socat - UNIX-CONNECT:/run/zincati/public/metrics.promsock
  @@ -29,6 +29,6 @@ zincati_update_agent_updates_enabled 1
  ```
  Additionally, the local Unix-domain socket can be proxied to HTTP and exposed to Prometheus.
  -For an example of such setup, check the [local\_exporter] repository.
  +For an example of such setup, check the [local\_exporter][local_exporter] repository.
  [local_exporter]: https://github.com/lucab/local_exporter
  