Remove extra semicolon.

services/web/public/stylesheets/core/ol-variables.less

@@ -109,7 +109,7 @@
 @sidebar-hover-bg               : @ol-blue-gray-4;
 @sidebar-hover-text-decoration  : none;
 
-@folders-menu-margin            : 0 -(@grid-gutter-width / 2);;
+@folders-menu-margin            : 0 -(@grid-gutter-width / 2);
 @folders-menu-line-height       : @structured-list-line-height;
 @folders-menu-item-v-padding    : (@line-height-computed / 4);
 @folders-menu-item-h-padding    : (@grid-gutter-width / 2);