Present window without timestamp; fix #5923

We were presenting the main window with an erroneous timestamp, which
was causing composer windows to be created with an incorrect z order.
This presents the window without a timestamp, so there's no room for
error.

src/client/geary-application.vala

@@ -123,7 +123,7 @@ along with Geary; if not, write to the Free Software Foundation, Inc.,
     private async void do_activate_async(owned string[] args) {
         // If Geary is already running, show the main window and return.
         if (controller != null && controller.main_window != null) {
-            controller.main_window.present_with_time((uint32) TimeVal().tv_sec);
+            controller.main_window.present();
             handle_args(args);
             return;
         }