[disko] no encrypted swap when encryption disabled

machines/modules/disko/default.nix

@@ -102,7 +102,7 @@ in
                     mountOptions = [ "umask=0077" ];
                   };
                 };
-                encryptedSwap = {
+                encryptedSwap = lib.mkIf cfg.encryption {
                   size = cfg.root.swap;
                   content =  {
                     type = "swap";