ENGCOM-1902: [Backport] chore: remove unused less import #15920

Author: Stanislav Idolov

lib/web/css/docs/source/docs.less

@@ -21,7 +21,6 @@
 @import '_icons.less';
 @import '_loaders.less';
 @import '_messages.less';
-//@import 'navigation.less';
 @import '_layout.less';
 @import '_pages.less';
 @import '_popups.less';