remove unnecessary styles

packages/app/src/styles/_sidebar.scss

@@ -344,9 +344,3 @@
     }
   }
 }
-
-.dropdown-menu {
-  // set larger number of z-index set to .grw-sidebar than
-  // the z-index of .grw-sidebar with and without .grw-sidebar-drawer which are relatively 1032 and 1020
-  z-index: 1040 !important;
-}