Revert "backend-x11: Take the touch grab on the stage window"

This reverts commit 3b85e4b2b9.

This breaks touch support; reverting would break wayland
(is what this patch tried to fix; we should find a better solution
that works on both).

src/core/display.c

@@ -877,8 +877,6 @@ meta_display_open (void)
 
   enable_compositor (display);
 
-  meta_backend_compositor_created (meta_get_backend ());
-
   meta_screen_create_guard_window (screen);
 
   /* Set up touch support */