Fix DNS wording and WireGuard protocol in external services table (#210)

* Initial plan

* Fix DNS wording and WireGuard protocol in external services table

- Changed "Public or private DNS address" to "DNS address" in Name resolution row
- Changed protocol from TCP to UDP for port 55820 in Cluster VPN row

Co-authored-by: DavidePrincipi <[email protected]>

* Update system_requirements.rst

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: DavidePrincipi <[email protected]>
Co-authored-by: Davide Principi <[email protected]>

Author: Copilot

system_requirements.rst

@@ -184,8 +184,8 @@ over TCP port 443.
 .. csv-table:: External services and endpoints required by NS8
    :header: "Purpose", "Host name", "Port", "Protocol", "Notes"
 
-   "Name resolution", "<DNS address>", "53", "UDP/TCP", "Public or private DNS address"
-   "Cluster VPN and node communication", "<leader node address>", "55820", "TCP", "Inter-node VPN and cluster traffic"
+   "Name resolution", "<Name server address>", "53", "UDP/TCP", "IP address of primary and, optionally, secondary DNS servers"
+   "Cluster VPN and node communication", "<leader node address>", "55820", "UDP", "Inter-node VPN and cluster traffic"
    "Cluster-admin leader API", "<leader node address>", "443", "HTTPS", "Join a new worker to the cluster"
    "OS and NS8 repositories mirror resolution", "mirrorlist.nethserver.org", "80", "HTTP", "Used to resolve Rocky Linux and NS8 mirrors"
    "Rocky Linux DNF repositories", "u4.nethesis.it, u5.nethesis.it", "443", "HTTPS", "Rocky Linux BaseOS and AppStream updates"