message: doc: Fix chicony doc. Use 'unmounted' word instead of 'umounted'
diff: ### Power off sequence
  -- under Linux open a terminal and type ***sudo poweroff***. This will safely power off the Raspberry Pi and ensure that the SD card is properly umounted
  +- under Linux open a terminal and type ***sudo poweroff***. This will safely power off the Raspberry Pi and ensure that the SD card is properly unmounted
  - remove the 5V supply from the Raspberry Pi
  - remove the 5V supply (micro USB cable) from the interposer
  