tests/kconfig_features: remove board whitelist
tests/kconfig_features: remove board whitelist

Now that all boards/cpus are migrated to Kconfig, we don't need this list anymore and it will enforce new boards to be adapted as well

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