Fix compiler error for ESP32-C3

Compile error on ESP32-C3 for even simplest example [simple_server](https://github.com/me-no-dev/ESPAsyncWebServer/tree/master/examples/simple_server)

```
/home/kh/Arduino/libraries/ESPAsyncWebServer-master/src/AsyncWebSocket.cpp: In member function 'IPAddress AsyncWebSocketClient::remoteIP()':
/home/kh/Arduino/libraries/ESPAsyncWebServer-master/src/AsyncWebSocket.cpp:843:28: error: call of overloaded 'IPAddress(unsigned int)' is ambiguous
         return IPAddress(0U);
                            ^
```

Author: khoih-prog

src/AsyncWebSocket.cpp

@@ -840,7 +840,7 @@ void AsyncWebSocketClient::binary(AsyncWebSocketMessageBuffer * buffer)
 
 IPAddress AsyncWebSocketClient::remoteIP() {
     if(!_client) {
-        return IPAddress(0U);
+        return IPAddress((uint32_t) 0);
     }
     return _client->remoteIP();
 }