Remove a superfluous const added in fa8b6ee.

The LayoutType is being returned by value so there is no need for the first
const. This silences approx 60 warning while compiling the plugins.

Author: Paul Harrison

mythtv/libs/libmythui/mythuibuttonlist.h

@@ -152,7 +152,7 @@ class MUI_PUBLIC MythUIButtonList : public MythUIType
 
     uint ItemWidth(void);
     uint ItemHeight(void);
-    const LayoutType GetLayout() const { return m_layout; }
+    LayoutType GetLayout() const { return m_layout; }
 
     bool MoveItemUpDown(MythUIButtonListItem *item, bool up);