[glib] docs: Fix incorrect macro name in GType tutorial

[Philip Withnall <pwithnall src gnome org>]

commit 121b1e5215eb4112e9bd905334d8af2161543764
Author: Philip Withnall <withnall endlessm com>
Date:   Thu Oct 5 15:40:14 2017 +0100

    docs: Fix incorrect macro name in GType tutorial
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770459

 docs/reference/gobject/tut_gtype.xml |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/docs/reference/gobject/tut_gtype.xml b/docs/reference/gobject/tut_gtype.xml
index 126eac3..a1c6005 100644
--- a/docs/reference/gobject/tut_gtype.xml
+++ b/docs/reference/gobject/tut_gtype.xml
@@ -677,7 +677,7 @@ viewer_editable_save (ViewerEditable  *self,
   g_return_if_fail (VIEWER_IS_EDITABLE (self));
   g_return_if_fail (error == NULL || *error == NULL);
 
-  iface = VIEWER_EDITABLE_GET_INTERFACE (self);
+  iface = VIEWER_EDITABLE_GET_IFACE (self);
   g_return_if_fail (iface->save != NULL);
   iface->save (self);
 }