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/utils/selection_handlers.dart

@@ -43,6 +43,7 @@ void handleShareAssets(
       return const ShareDialog();
     },
     barrierDismissible: false,
+    useRootNavigator: false,
   );
 }