[Doc][Newsfeed] Type issue with useFragment when separating news feed content to fragment

In the new Relay tutorial, section ["Connections & Pagination"](https://relay.dev/docs/tutorial/connections-pagination/#step-3--lower-newsfeed-into-a-fragment), the example code will produce typing issue as it didn't provide necessary types for the news feed content separated from the original query.

Instead of
```
export default function Newsfeed() {
const queryData = useLazyLoadQuery(NewsfeedFragment, {});
const data = useFragment(NewsfeedContentsFragment, queryData);
const storyEdges = data.newsfeedStories.edges;
...
}
```

It should be
```
import type {NewsfeedQuery as NewsfeedQueryType} from './__generated__/NewsfeedQuery.graphql';
import type {NewsfeedContentsFragment$key} from './__generated__/NewsfeedContentsFragment.graphql';
...
export default function Newsfeed() {
const queryData = useLazyLoadQuery(NewsfeedQuery, {});
const data = useFragment(NewsfeedContentsFragment, queryData);
const storyEdges = data.viewer.newsfeedStories.edges;
...
```