message: [dbus] remove debug log
diff: @@ -930,13 +930,10 @@ otError DBusThreadObject::GetExternalRoutesHandler(DBusMessageIter &aIter)
  externalRouteTable.push_back(route);
  }
  - printf("Encode size %zu\n", externalRouteTable.size());
  -
  VerifyOrExit(DBusMessageEncodeToVariant(&aIter, externalRouteTable) == OTBR_ERROR_NONE,
  error = OT_ERROR_INVALID_ARGS);
  exit:
  - printf("error %d\n", error);
  return error;
  }
  