tests/pkg_fatfs_vfs: blacklist nucleo-l031k6
tests/pkg_fatfs_vfs: blacklist nucleo-l031k6

Adding the extra prints to the hard fault handler bumped this test over
the available ROM for this board

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