[gtkmm-documentation] ScaleButton example: Correct the use of icons.

[Murray Cumming <murrayc src gnome org>]

commit 14833b2940123adb5f913a986a36dc26dcdac5d7
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Feb 2 13:13:34 2015 +0100

    ScaleButton example: Correct the use of icons.
    
    set_value("Some Value") was not appropriate because it wants
    to show an appropriate icon based on set_icons().

 examples/book/buttons/scalebutton/examplewindow.cc |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)
---
diff --git a/examples/book/buttons/scalebutton/examplewindow.cc 
b/examples/book/buttons/scalebutton/examplewindow.cc
index 7bc6516..911db56 100644
--- a/examples/book/buttons/scalebutton/examplewindow.cc
+++ b/examples/book/buttons/scalebutton/examplewindow.cc
@@ -30,13 +30,11 @@ ExampleWindow::ExampleWindow()
   set_border_width(12);
 
   std::vector<Glib::ustring> icons;
-  icons.push_back("audio-volume-high");
   icons.push_back("audio-volume-low");
+  icons.push_back("audio-volume-high");
   icons.push_back("audio-volume-medium");
   m_button.set_icons(icons);
 
-  m_button.set_label("Some Value");
-
   add(m_grid);
   m_grid.set_vexpand(true);
   m_grid.set_hexpand(true);