Progressbars: use default frame thickness

It's unnecessary overhead to set the value everywhere, except it's needed.

src/driver/volume.cpp

@@ -113,6 +113,7 @@ void CVolume::Init()
 		delete volscale;
 	volscale = new CProgressBar(progress_x, progress_y, progress_w, progress_h, colFrame, colBar, colShadow, COL_MENUCONTENT_PLUS_3, COL_MENUCONTENT_PLUS_1, true);
 	volscale->setInvert();
+	volscale->setFrameThickness(2);
 
 	// mute icon
 	mute_icon_dx 	= 0;