add missing config for SFT federation [skip ci]

Author: Veki301

values/sftd/prod-values.example.yaml

@@ -12,4 +12,6 @@ tls:
 #   enabled: true
 #   discoveryRequired: false
 #   turnServerURI: "turn:coturn.public.ip.address:3478?transport=udp"
-#   secret: "coturn_zrest_secret"
+#   secret: "coturn_zrest_secret"
+# Turn on secondary IP listener (for internal IP) when using federation
+# internalIpListener: false