revert buffer size bar back to white

src/scss/skin-super-modern/components/_seekbar.scss

@@ -67,7 +67,7 @@ $seekbar-height: .3125em;
 
     .#{$prefix}-seekbar-bufferlevel {
       @extend %bar;
-      background-color: transparentize($color-secondary, .3);
+      background-color: $color-primary;
       margin: $bar-inset 0;
       transition: .3s linear, .3s linear;
       transition-property: transform;