Don't depend upon @syntax-cursor-line

Summary: This variable is specific to the one-light/one-dark themes. Compiling the less will crash if you try to use a different theme, for example: Atom Dark.

Reviewed By: sunz7

Differential Revision: D10258614

fbshipit-source-id: da419c58cf0d2892abc00561714ad85fd258fc85

Author: captbaritone

pkg/nuclide-scrollbar-indicators/styles/scroll-indicators.less

@@ -50,7 +50,7 @@ atom-text-editor:not(.nuclide-wrapped-editor) /deep/ ::-webkit-scrollbar {
   width: 12px;
 
   &-thumb:vertical {
-    background-color: @syntax-cursor-line; // mix(@syntax-background-color, @syntax-cursor-color);
+    background-color: hsla(220, 100%,  80%, .04);
     z-index: 5;
   }