IPAddress missing definition of operator!=()

This was already fixed in ArduinoCore-API:
* https://github.com/arduino/Arduino/issues/7336
* https://github.com/arduino/ArduinoCore-API/commit/d5ae3faba1d69500f920c57b2afac59021831278