Update out of date comments in aws-hyper lib (#433)

            // Create a new request-scoped policy

            .retry(self.retry_handler.new_handler())

            .layer(ParseResponseLayer::<O, Retry>::new())

            // These layers can be considered as occuring in order, that is:

            // 1. Resolve an endpoint

            // 2. Add a user agent

            // 3. Sign

            // 4. Dispatch over the wire

            .layer(endpoint_resolver)

            .layer(user_agent)

            .layer(signer)

            // Apply the user agent _after signing_. We should not sign the user-agent header

            .layer(DispatchLayer::new())

            .service(inner);

        svc.ready().await?.call(input).await