tests/bench_xtimer: add arduino-nano-33-iot to low memory
tests/bench_xtimer: add arduino-nano-33-iot to low memory

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