replace individual bridge option by common one

modules/nix/containers/nixos/traefik.nix

@@ -11,10 +11,6 @@ in
       default = false;
       description = "traefik nixos ct";
     };
-    bridge = mkOption {
-      type = types.str;
-      description = "the bridge to use e.g. (br0)";
-    };
     ip = mkOption {
       type = types.str;
       description = "ip addr e.g. (192.168.1.20)";