refactor: remove duplicate css declaration

(cherry picked from commit 18ca598)

Author: donroyco

src/app/pages/component-sidenav/component-sidenav.scss

@@ -131,7 +131,6 @@ app-component-sidenav {
       box-sizing: border-box;
       margin: 0;
       max-height: initial;
-      box-sizing: border-box;
     }
   }
 }