util: Don't check whether zenity supports options

Doing this synchronously means that zenity tries to initialize GTK+.
Under Wayland, that will try to connect back to mutter as a display
server. We're waiting on zenity to exit, and zenity is waiting for
a connection response. Deadlock.

Simply assume that zenity will support all the options we feed it,
since it should be the correct version. Perhaps we should replace
our use of zenity with a simple helper binary that we know will
have all the right options if this still isn't good enough.