[mutter] compositor: Remove unused background_actor private reference

[Carlos Garnacho <carlosg src gnome org>]

commit 736cac43e9de63c09e86e52db6793c3ef6b4ca01
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Mon Apr 29 15:04:43 2019 -0500

    compositor: Remove unused background_actor private reference
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/556

 src/compositor/compositor-private.h | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/src/compositor/compositor-private.h b/src/compositor/compositor-private.h
index 6ab33416c..b08746d24 100644
--- a/src/compositor/compositor-private.h
+++ b/src/compositor/compositor-private.h
@@ -27,7 +27,6 @@ struct _MetaCompositor
   guint           server_time_is_monotonic_time : 1;
 
   ClutterActor          *stage, *window_group, *top_window_group, *feedback_group;
-  ClutterActor          *background_actor;
   GList                 *windows;
   Window                 output;