disable nix firewall by default

nixos/files/configuration.nix

@@ -67,7 +67,7 @@
   # networking.firewall.allowedTCPPorts = [ ... ];
   # networking.firewall.allowedUDPPorts = [ ... ];
   # Or disable the firewall altogether.
-  # networking.firewall.enable = false;
+  networking.firewall.enable = false;
 
   # Define a user account. Don't forget to set a password with ‘passwd’.
   # users.extraUsers.guest = {