[gtk] Widget: Trivially fix arg name in non-doc comment

[Daniel Boles <dboles src gnome org>]

commit ae14fa4efdec72668828e5e0c68d7beab759dcae
Author: Daniel Boles <dboles src gmail com>
Date:   Sun Apr 22 21:07:50 2018 +0100

    Widget: Trivially fix arg name in non-doc comment

 gtk/gtkwidget.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 9dc5dd55ff..6e0183d405 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -6716,7 +6716,7 @@ gtk_widget_is_sensitive (GtkWidget *widget)
 
 
 /* Insert @widget into the children list of @parent,
- * after @previous_child */
+ * after @previous_sibling */
 static void
 gtk_widget_reposition_after (GtkWidget *widget,
                              GtkWidget *parent,