Compiling for RP2350 is broken

While the RP2040 boards are supported and working, the compilation breaks when RP2350 based boards selected. The k3ng_keyer.ino needs to receive this update:

`#elif defined(ARDUINO_ARCH_MBED) || defined(ARDUINO_RASPBERRY_PI_PICO_W) || defined(ARDUINO_RASPBERRY_PI_PICO) || defined(ARDUINO_RASPBERRY_PI_PICO_2) || defined(ARDUINO_RASPBERRY_PI_PICO_2W)`