Remove unused imports from window

src/briar/gtk/window.py

@@ -9,7 +9,7 @@ from briar.gtk.define import App
 
 import gi
 gi.require_version('Gtk', '3.0')
-from gi.repository import Gtk, Gdk, GLib
+from gi.repository import Gtk
 
 
 class Window(Gtk.ApplicationWindow):