fix(mobile): share asset back button exit application (#18919)

* fix(mobile): remove dialog wrapper around share asset

* removed from multiple share and delete share dialog class

* Revert change to ShareDialog and useRootNavigator: false for showDialog

mobile/lib/providers/asset_viewer/download.provider.dart

@@ -186,6 +186,7 @@ class DownloadStateNotifier extends StateNotifier<DownloadState> {
         return const ShareDialog();
       },
       barrierDismissible: false,
+      useRootNavigator: false,
     );
   }
 }