boards/common/arduino-atmega: remove special case for jiminy-mega256rfr2
boards/common/arduino-atmega: remove special case for jiminy-mega256rfr2

The board is deprecated, no need to ignore this board anymore here.

Having the `arduino` and `periph_pwm` features is now required for all
boards using 'arduino-atmega' (as it was except for that board).

If this should change in the future, it should be defined either in each
arduino board, in another board common, or per CPU_MODEL.

toonst/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,OTAkeys/RIOT,ant9000/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,smlng/RIOT,OTAkeys/RIOT,miri64/RIOT,x3ro/RIOT,aeneby/RIOT,OTAkeys/RIOT,authmillenon/RIOT,authmillenon/RIOT,toonst/RIOT,toonst/RIOT,x3ro/RIOT,toonst/RIOT,mtausig/RIOT,yogo1212/RIOT,basilfx/RIOT,aeneby/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,ant9000/RIOT,OTAkeys/RIOT,x3ro/RIOT,toonst/RIOT,aeneby/RIOT,kaspar030/RIOT,authmillenon/RIOT,josephnoir/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OlegHahm/RIOT,x3ro/RIOT,OlegHahm/RIOT,aeneby/RIOT,mtausig/RIOT,jasonatran/RIOT,basilfx/RIOT,basilfx/RIOT,kaspar030/RIOT,yogo1212/RIOT,jasonatran/RIOT,smlng/RIOT,basilfx/RIOT,authmillenon/RIOT,mtausig/RIOT,kYc0o/RIOT,mtausig/RIOT,yogo1212/RIOT,basilfx/RIOT,authmillenon/RIOT,authmillenon/RIOT,x3ro/RIOT,mtausig/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,kYc0o/RIOT,kYc0o/RIOT,miri64/RIOT,jasonatran/RIOT,smlng/RIOT,josephnoir/RIOT,ant9000/RIOT,OlegHahm/RIOT,miri64/RIOT,aeneby/RIOT,ant9000/RIOT,smlng/RIOT,miri64/RIOT,kYc0o/RIOT,smlng/RIOT,kaspar030/RIOT,kaspar030/RIOT,yogo1212/RIOT,miri64/RIOT,jasonatran/RIOT,josephnoir/RIOT