[libdazzle] util: fix return type annotation

[Christian Hergert <chergert src gnome org>]

commit 471657586c8a904905c5e2bb010f2c593c3b5ce6
Author: Christian Hergert <chergert redhat com>
Date:   Sun Nov 12 01:56:47 2017 -0800

    util: fix return type annotation

 src/util/dzl-gtk.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/src/util/dzl-gtk.c b/src/util/dzl-gtk.c
index cf2d7ae..b289cad 100644
--- a/src/util/dzl-gtk.c
+++ b/src/util/dzl-gtk.c
@@ -217,6 +217,16 @@ dzl_gtk_widget_find_child_typed_cb (GtkWidget *widget,
     }
 }
 
+/**
+ * dzl_gtk_widget_find_child_typed:
+ *
+ * Tries to locate a widget in a hierarchy given it's #GType.
+ *
+ * There is not an efficient implementation of this method, so use it
+ * only when the hierarchy of widgets is small.
+ *
+ * Returns: (transfer none) (type Gtk.Widget) (nullable): A widget or %NULL
+ */
 gpointer
 dzl_gtk_widget_find_child_typed (GtkWidget *widget,
                                  GType      child_type)