[gtk+] Fix a typo in the docs

[Matthias Clasen <matthiasc src gnome org>]

commit 2d85e8df8b178a4bcbf376ff02d19326e85ef309
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Dec 6 23:39:27 2017 -0500

    Fix a typo in the docs

 gtk/gtktreesortable.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtktreesortable.h b/gtk/gtktreesortable.h
index c08e6a2..bb49682 100644
--- a/gtk/gtktreesortable.h
+++ b/gtk/gtktreesortable.h
@@ -48,7 +48,7 @@ G_BEGIN_DECLS
 /**
  * GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID:
  *
- * The GTK_TREE_SORTABLE_DEFAULT_SORT_COLUMN_ID can be used to make a
+ * The GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID can be used to make a
  * #GtkTreeSortable use no sorting.
  *
  * See also gtk_tree_sortable_set_sort_column_id()