kstyle: Make scrollbar handles slightly skinnier

Changed handle thickness from 10px to 8px. This makes the spacing around
the handle look more consistent. Visually, there was 5px of empty space
on each side, now there is 6px of empty space on each side.


(cherry picked from commit 2f92640270)

kstyle/breezemetrics.h

@@ -90,7 +90,7 @@ namespace Breeze
 
         // scrollbars
         static constexpr int ScrollBar_Extend = 21;
-        static constexpr int ScrollBar_SliderWidth = 10;
+        static constexpr int ScrollBar_SliderWidth = 8;
         static constexpr int ScrollBar_MinSliderHeight = 20;
         static constexpr int ScrollBar_NoButtonHeight = (ScrollBar_Extend-ScrollBar_SliderWidth)/2;
         static constexpr int ScrollBar_SingleButtonHeight = ScrollBar_Extend;