Fix doc referencing incorrect variable `details` (#2487)

The variable name that's loading is called `user`

content/docs/concurrent-mode-suspense.md

@@ -360,7 +360,7 @@ This `resource` object represents the data that isn't there yet, but might event
 
 **As more data streams in, React will retry rendering, and each time it might be able to progress "deeper".** When `resource.user` is fetched, the `<ProfileDetails>` component will render successfully and we'll no longer need the `<h1>Loading profile...</h1>` fallback. Eventually, we'll get all the data, and there will be no fallbacks on the screen.
 
-This has an interesting implication. Even if we use a GraphQL client that collects all data requirements in a single request, *streaming the response lets us show more content sooner*. Because we render-*as-we-fetch* (as opposed to *after* fetching), if `details` appear in the response earlier than `posts`, we'll be able to "unlock" the outer `<Suspense>` boundary before the response even finishes. We might have missed this earlier, but even the fetch-then-render solution contained a waterfall: between fetching and rendering. Suspense doesn't inherently suffer from this waterfall, and libraries like Relay take advantage of this.
+This has an interesting implication. Even if we use a GraphQL client that collects all data requirements in a single request, *streaming the response lets us show more content sooner*. Because we render-*as-we-fetch* (as opposed to *after* fetching), if `user` appear in the response earlier than `posts`, we'll be able to "unlock" the outer `<Suspense>` boundary before the response even finishes. We might have missed this earlier, but even the fetch-then-render solution contained a waterfall: between fetching and rendering. Suspense doesn't inherently suffer from this waterfall, and libraries like Relay take advantage of this.
 
 Note how we eliminated the `if (...)` "is loading" checks from our components. This doesn't only remove boilerplate code, but it also simplifies making quick design changes. For example, if we wanted profile details and posts to always "pop in" together, we could delete the `<Suspense>` boundary between them. Or we could make them independent from each other by giving each *its own* `<Suspense>` boundary. Suspense lets us change the granularity of our loading states and orchestrate their sequencing without invasive changes to our code.