Example of using aws-amplify for lambda->graphql

**Describe the content issue**:
The example given uses pretty low level and verbose code (http requests?) to generate a request from lambda to graphql using IAM.

It would seem to me that it should be possible to do something like:
```

Amplify.configure(config)
const client=generateClient({authMode: "iam"})
const response = await client.graphql({
query: queries.listCollisions,
})
return response.data.listCollisions.items;

```

**URL page where content issue is**:
https://docs.amplify.aws/javascript/build-a-backend/graphqlapi/connect-from-server-runtime/#iam-authorization

Open the IAM authorization section at the linked documentation URL and compare the existing Lambda-to-GraphQL example with the requested Amplify client approach. Confirm the example's placement and conventions, then update the page so the documented flow is clear and complete for this use case.

Written by the indexing model from the issue text.