[ai] Update example in README.md (#525)

## Summary
Update example in README.md. It was using an outdated option, so this
makes it up-to-date.

## How was it tested?
Ran the code manually.

## Community Contribution License

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project maintainers under the terms of the [Apache 2
License](https://www.apache.org/licenses/LICENSE-2.0).

By creating this pull request I represent that I have the right to
license the contributions to the project maintainers under the Apache 2
License as stated in the [Community Contribution
License](https://github.com/jetify-com/opensource/blob/main/CONTRIBUTING.md#community-contribution-license).

Author: loreto

aisdk/ai/README.md

@@ -98,13 +98,13 @@ func main() {
         context.Background(),
         "Explain quantum computing in simple terms",
         ai.WithModel(model),
-        ai.WithMaxTokens(200),
+        ai.WithMaxOutputTokens(200),
     )
     if err != nil {
         log.Fatal(err)
     }
-
     // Do whatever you want with the response...
+    fmt.Println(response)
 }
 ```