[Gtk] Rename FileDialog folder selection button
[Gtk] Rename FileDialog folder selection button

Other folder actions with Gtk stock ids have only one word to
describe the button action, like Create, Save, Open.

mono/xwt,hwthomas/xwt,antmicro/xwt,hamekoz/xwt,lytico/xwt,TheBrainTech/xwt,cra0zy/xwt