Copyedit and fix typos in Gitaly admin docs

seperate => separate
Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

doc/administration/gitaly/index.md

@@ -195,12 +195,12 @@ authentication](https://gitlab.com/gitlab-org/gitaly/blob/master/doc/configurati
    gitlab_workhorse['enable'] = false
    grafana['enable'] = false
 
-   # If you run a seperate monitoring node you can disable these services
+   # If you run a separate monitoring node you can disable these services
    alertmanager['enable'] = false
    prometheus['enable'] = false
 
-   # If you don't run a seperate monitoring node you can
-   # Enable Prometheus access & disable these extra services
+   # If you don't run a separate monitoring node you can
+   # enable Prometheus access & disable these extra services.
    # This makes Prometheus listen on all interfaces. You must use firewalls to restrict access to this address/port.
    # prometheus['listen_address'] = '0.0.0.0:9090'
    # prometheus['monitor_kubernetes'] = false