[gtk+] notebook: Update CSS docs

[Matthias Clasen <matthiasc src gnome org>]

commit c283315466bfba84e99b17be13a31275ffd40eb1
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Nov 9 13:33:58 2015 -0500

    notebook: Update CSS docs
    
    The .header style class is no longer used.

 gtk/gtknotebook.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index 9e1d711..7b8337e 100644
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -124,9 +124,8 @@
  * to the tabs node. If the notebook is scrollable, CSS nodes with
  * name arrow are placed as first and last child of the tabs node.
  *
- * The main node gets the .frame style class when rendering the
- * background of a notebook with border. It gets the .header
- * style class for rendering the tab area background.
+ * The main node gets the .frame style class when the notebook
+ * has a border (see gtk_notebook_set_has_border()).
  *
  * The header node gets one of the style class .top, .bottom,
  * .left or .right, depending on where the tabs are placed. For