pkg/nanopb: bump version to 0.4.4
pkg/nanopb: bump version to 0.4.4

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