fixed typo in comment for assets.scss

cms/static/sass/views/_assets.scss

@@ -325,7 +325,7 @@
     }
   }
 
-  // uses similar styling as assets.scss, static-pages.scss 
+  // uses similar styling as unit.scss, static-pages.scss
   .action-item {
     display: inline-block;
     margin: ($baseline/4) 0 ($baseline/4) ($baseline/4);