style: Correct the styling for sliders
style: Correct the styling for sliders

The slider handle is now smaller, so make sure the border-image
slices match.

jonnylamb/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx