cpu/esp32: remove periph_rtc from used modules
cpu/esp32: remove periph_rtc from used modules

`periph_rtc` is no longer used by default.
OTAkeys/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,basilfx/RIOT,kaspar030/RIOT,smlng/RIOT,kYc0o/RIOT,OlegHahm/RIOT,smlng/RIOT,authmillenon/RIOT,OTAkeys/RIOT,miri64/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,kaspar030/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,authmillenon/RIOT,ant9000/RIOT,RIOT-OS/RIOT,basilfx/RIOT,ant9000/RIOT,yogo1212/RIOT,basilfx/RIOT,miri64/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,jasonatran/RIOT,yogo1212/RIOT,authmillenon/RIOT,smlng/RIOT,ant9000/RIOT,smlng/RIOT,yogo1212/RIOT,yogo1212/RIOT,miri64/RIOT,jasonatran/RIOT,kYc0o/RIOT,kYc0o/RIOT,miri64/RIOT,authmillenon/RIOT,kYc0o/RIOT,OTAkeys/RIOT,kaspar030/RIOT,OlegHahm/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,OTAkeys/RIOT,authmillenon/RIOT,smlng/RIOT,basilfx/RIOT,basilfx/RIOT,kYc0o/RIOT,yogo1212/RIOT,miri64/RIOT