ui_init: Remove duplicate user sidebar build call.

`message_view.show` already calls and ideally should call
activity_ui.build_user_sidebar, so this call is not needed here.

web/src/ui_init.js

@@ -548,7 +548,6 @@ export function initialize_everything(state_data) {
                 ],
                 {trigger},
             );
-            activity_ui.build_user_sidebar();
         },
     });
     stream_list_sort.initialize();