Update docs very briefly, concisely, and surgically to clarify setting wlan to appropriate country (e.g., US for United States, CA for Canada, DE for germany)

[sgbaird]

just want to add for troubleshooting wifi setup with raspberry pi. i didnt set my wlan country to CA and this gave me some problems. what was happening was it was blocking the wifi connection. when i ran: rfkill list all the wifi showed up as soft blocked. getting around this would be to run: sudo rfkill unblock wifi which would unblock it, but when you restart the networkmanager, it would just be blocked again. After i set the wlan country to CA, it stopped reblocking the wifi

per note by @kelvinchow23 in #183 (comment)

Very specifically I think it's this one https://ac-training-lab.readthedocs.io/en/latest/raspberry-pi-wpa2-enterprise.html