Optimize iOS full-screen back gesture implementation (#643)

* Optimize iOS full-screen back gesture implementation

- Fix #613 and #617

* Fix setting page

lib/pages/aggregated_search_page.dart

@@ -170,7 +170,6 @@ class _SliverSearchResultState extends State<_SliverSearchResult>
             text: widget.keyword,
             sourceKey: widget.source.key,
           ),
-          iosFullScreenGesture: false,
         );
       },
       child: Column(