docs: update testing example to check data (TanStack#2664)

Author: Ehesp

docs/src/pages/guides/testing.md

@@ -121,7 +121,7 @@ await waitFor(() => {
   return result.current.isSuccess;
 });
 
-expect(result.current).toEqual({answer: 42});
+expect(result.current.data).toEqual({answer: 42});
 ```
 
 Here we are making use of `waitFor` and waiting until our the query status indicates that the request has succeeded. This way we know that our hook has finished and should have the correct data.