Revert "Fix syntax error in nixos/lib/build-vms.nix, introduced by 86c0f8c"

This reverts commit 704e91bab005eabe968a3b140222fb0cf7afd4db.

nixos/lib/build-vms.nix

···
                   [ { address = "192.168.${toString first}.${toString m.second}";
                       prefixLength = 24;
                   } ];
-                });
+                }
             in
             { key = "ip-address";
               config =