Ethernet defines SSID_MAX_LENGTH

[ddmesh]

https://github.com/arduino/ArduinoCore-mbed/blob/dd5abb6171063b2777620b9339510c63b915ce72/libraries/Ethernet/src/Ethernet.cpp#L3C9-L3C24

Question: why is this defined here and never used? should be removed

[pennam]

Fixed by #901