[mutter] background-content: Shut up warning

[Florian Müllner <fmuellner src gnome org>]

commit 932340a989554b56bae69f3403dca7c4edda2676
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Jun 10 10:40:45 2020 +0200

    background-content: Shut up warning
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1303

 src/compositor/meta-background-content.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/compositor/meta-background-content.c b/src/compositor/meta-background-content.c
index 13c9e85c51..daecf2676e 100644
--- a/src/compositor/meta-background-content.c
+++ b/src/compositor/meta-background-content.c
@@ -807,7 +807,7 @@ meta_background_content_init (MetaBackgroundContent *self)
  *
  * Creates a new actor to draw the background for the given monitor.
  *
- * Return value: the newly created background actor
+ * Return value: (transfer full): the newly created background actor
  */
 ClutterContent *
 meta_background_content_new (MetaDisplay *display,