examples: Drop a redundant frame

The frame in the drawing example adds nothing
and looks wrong.

examples/drawing.c

@@ -132,7 +132,6 @@ activate (GtkApplication *app,
           gpointer        user_data)
 {
   GtkWidget *window;
-  GtkWidget *frame;
   GtkWidget *drawing_area;
   GtkGesture *drag;
   GtkGesture *press;
@@ -142,14 +141,11 @@ activate (GtkApplication *app,
 
   g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
 
-  frame = gtk_frame_new (NULL);
-  gtk_window_set_child (GTK_WINDOW (window), frame);
-
   drawing_area = gtk_drawing_area_new ();
   /* set a minimum size */
   gtk_widget_set_size_request (drawing_area, 100, 100);
 
-  gtk_frame_set_child (GTK_FRAME (frame), drawing_area);
+  gtk_window_set_child (GTK_WINDOW (window), drawing_area);
 
   gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (drawing_area), draw_cb, NULL, NULL);