Don't show url_status_box on start

This isn't a big issue on desktop. But on mobile, handle_motion is never
triggered and an empty url_status_box is always visible.

Author: chuangzhu

data/resources/ui/window.blp

@@ -100,6 +100,7 @@ template GeopardWindow: Adw.ApplicationWindow {
         orientation: vertical;
         valign: end;
         Gtk.Box url_status_box {
+          visible: false;
           styles ["background"]
           Gtk.Label url_status {
             xalign: 0.0;