boards/microbit: doc: FLASHTOOL -> PROGRAMMER
boards/microbit: doc: FLASHTOOL -> PROGRAMMER

kYc0o/RIOT,OTAkeys/RIOT,jasonatran/RIOT,ant9000/RIOT,OlegHahm/RIOT,miri64/RIOT,miri64/RIOT,authmillenon/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,kYc0o/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,ant9000/RIOT,kaspar030/RIOT,OTAkeys/RIOT,miri64/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,jasonatran/RIOT,kaspar030/RIOT,authmillenon/RIOT,kaspar030/RIOT,kaspar030/RIOT,ant9000/RIOT,authmillenon/RIOT,jasonatran/RIOT,authmillenon/RIOT,jasonatran/RIOT,miri64/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,ant9000/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,authmillenon/RIOT,OlegHahm/RIOT,miri64/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kYc0o/RIOT,OTAkeys/RIOT,kYc0o/RIOT,ant9000/RIOT