pty: Removed unused variable
pty: Removed unused variable

Fallout from b59d76a5073d789f2f948cf928e883cb70cc8a75

https://bugzilla.gnome.org/show_bug.cgi?id=782977

thestinger/vte-ng,thestinger/vte-ng,thestinger/vte-ng,saitoha/vte-sixel,saitoha/vte-sixel,saitoha/vte-sixel