[mutter] clutter/cogl/stage: Remove duplicate region union

[Jonas Ådahl <jadahl src gnome org>]

commit 71101cab82e1e6da0e9798c752a0e7610fc778a3
Author: Sebastian Keller <skeller gnome org>
Date:   Wed Feb 26 00:45:48 2020 +0100

    clutter/cogl/stage: Remove duplicate region union
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/1089

 clutter/clutter/cogl/clutter-stage-cogl.c | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/clutter/clutter/cogl/clutter-stage-cogl.c b/clutter/clutter/cogl/clutter-stage-cogl.c
index ede58e6eb..530ac1306 100644
--- a/clutter/clutter/cogl/clutter-stage-cogl.c
+++ b/clutter/clutter/cogl/clutter-stage-cogl.c
@@ -751,7 +751,6 @@ clutter_stage_cogl_redraw_view (ClutterStageWindow *stage_window,
 
               /* Update the redraw clip region with the extra damage. */
               cairo_region_union (redraw_clip, view_damage);
-              cairo_region_union (redraw_clip, view_damage);
 
               cairo_region_destroy (view_damage);
               cairo_region_destroy (fb_damage);