Fix compiler warnings (-Wswitch-default)

Missed this one because it's in Windows code.

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>

src/oatpp/network/tcp/Connection.cpp

@@ -217,6 +217,8 @@ void Connection::setStreamIOMode(oatpp::data::stream::IOMode ioMode) {
       }
       m_mode = data::stream::ASYNCHRONOUS;
       break;
+    default:
+      break;
   }
 
 }