glib-2.0: Fix typo in FileSeek attribute
glib-2.0: Fix typo in FileSeek attribute

rvu95/vala,tjol/vala-tjol,Distrotech/vala,spidermonkdust/vala,frida/vala,flobrosch/vala-fixes,severinh/vala,spidermonkdust/vala,flobrosch/vala-fixes,Distrotech/vala,severinh/vala,jessevdk/vala,jessevdk/vala,xdave/pvala,playya/vala,severinh/vala,playya/vala,rvu95/vala,Distrotech/vala,GNOME/vala,frida/vala,rvu95/vala,GNOME/vala,flobrosch/vala-fixes,tjol/vala-tjol,spidermonkdust/vala,frida/vala,tjol/vala-tjol,GNOME/vala,frida/vala,GNOME/vala,jessevdk/vala,playya/vala,frida/vala