Add UPDATER_PERIOD to download fresh ProtonVPN server list

Will refresh gluetun's embedded server list from ProtonVPN API.
Need to extract public key for US-TX#253 (95.173.217.29) which
is not in gluetun's embedded database but should be in the live list.

servers/legion/k8s/media/fornax-workers.yaml

@@ -101,9 +101,11 @@ spec:
                   name: fornax-worker-tx253-secrets
                   key: PROTONVPN_PRIVATE_KEY
             - name: SERVER_NAMES
-              value: "US-FREE#33"
+              value: "US-TX#179"
             - name: VPN_PORT_FORWARDING
               value: "off"
+            - name: UPDATER_PERIOD
+              value: "2m"
             - name: DOT
               value: "off"
             - name: DNS_UPSTREAM_RESOLVER_TYPE