[gnome-boxes] style: icon-shadow -> -gtk-icon-shadow

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 77fee4ac8862b090e7206db70c900c7298fefba0
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Wed Dec 16 15:12:45 2015 +0000

    style: icon-shadow -> -gtk-icon-shadow
    
    'icon-shadow' CSS property has been renamed to '-gtk-icon-shadow'. Let's
    use the new property name to avoid a gtk+ warning at runtime.

 data/gtk-style.css |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/data/gtk-style.css b/data/gtk-style.css
index 0e77eed..9a5ec12 100644
--- a/data/gtk-style.css
+++ b/data/gtk-style.css
@@ -101,7 +101,7 @@ BoxesResourceGraph {
     background-image: none;
     font-weight: bold;
     text-shadow: none;
-    icon-shadow: none;
+    -gtk-icon-shadow: none;
     box-shadow: none;
     outline-color: alpha(currentColor, 0.15);
 }