[gtk+] demo: Remove an expose_event mention

[Timm Bäder <baedert src gnome org>]

commit 614c3e672125281b3ed7e0cb2160415be0105be1
Author: Timm Bäder <mail baedert org>
Date:   Mon Feb 5 11:52:32 2018 +0100

    demo: Remove an expose_event mention

 demos/gtk-demo/drawingarea.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/demos/gtk-demo/drawingarea.c b/demos/gtk-demo/drawingarea.c
index 7417862..985345d 100644
--- a/demos/gtk-demo/drawingarea.c
+++ b/demos/gtk-demo/drawingarea.c
@@ -4,8 +4,8 @@
  * of various kinds.
  *
  * This demo has two drawing areas. The checkerboard area shows
- * how you can just draw something; all you have to do is write
- * a signal handler for expose_event, as shown here.
+ * how you can just draw something; all you have to do is set a function
+ * via gtk_drawing_area_set_draw_func(), as shown here.
  *
  * The "scribble" area is a bit more advanced, and shows how to handle
  * events such as button presses and mouse motion. Click the mouse