boards/nrf52dk: fix broken links
boards/nrf52dk: fix broken links

OTAkeys/RIOT,authmillenon/RIOT,kYc0o/RIOT,basilfx/RIOT,yogo1212/RIOT,basilfx/RIOT,ant9000/RIOT,basilfx/RIOT,miri64/RIOT,ant9000/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,kaspar030/RIOT,basilfx/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,kYc0o/RIOT,kaspar030/RIOT,kYc0o/RIOT,basilfx/RIOT,ant9000/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,authmillenon/RIOT,authmillenon/RIOT,jasonatran/RIOT,yogo1212/RIOT,yogo1212/RIOT,miri64/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,yogo1212/RIOT,ant9000/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,yogo1212/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,miri64/RIOT,miri64/RIOT,ant9000/RIOT,kYc0o/RIOT,authmillenon/RIOT,authmillenon/RIOT,jasonatran/RIOT,jasonatran/RIOT,authmillenon/RIOT,miri64/RIOT