system: Always allow dnsmasq ports

Simplifies things a bit.

modules/system.nix

@@ -249,12 +249,10 @@ in
       };
 
       firewall = {
-        allowedUDPPorts =
-          optional phone [
+        allowedUDPPorts = [
           67
           68
-          ]
-          ++ optional allowSRB2Port [ 5029 ];
+        ] ++ optional allowSRB2Port [ 5029 ];
 
         allowedTCPPorts = mkIf allowDevPort [ 3000 ];
       };