riotboot: fix APP_VER default documentation
riotboot: fix APP_VER default documentation

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