[gtk+] Add gtk_image_get_surface to the docs

[Matthias Clasen <matthiasc src gnome org>]

commit b940872005c960ff3bb921121da812c467945581
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Oct 23 05:59:30 2017 +0200

    Add gtk_image_get_surface to the docs
    
    This was missed.

 docs/reference/gtk/gtk4-sections.txt |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/gtk4-sections.txt b/docs/reference/gtk/gtk4-sections.txt
index 8edf9fb..040f2ae 100644
--- a/docs/reference/gtk/gtk4-sections.txt
+++ b/docs/reference/gtk/gtk4-sections.txt
@@ -1487,6 +1487,7 @@ GtkIconViewPrivate
 GtkImage
 GtkImageType
 gtk_image_get_pixbuf
+gtk_image_get_surface
 gtk_image_get_animation
 gtk_image_get_icon_name
 gtk_image_get_gicon