Cleanup docs in Kafka Streams binder
Cleanup docs in Kafka Streams binder

 - Add StreamListener deprecation notice in docs

Resolves https://github.com/spring-cloud/spring-cloud-stream-binder-kafka/issues/1005

spring-cloud/spring-cloud-stream,garyrussell/spring-cloud-stream,garyrussell/spring-cloud-stream,spring-cloud/spring-cloud-stream,spring-cloud/spring-cloud-stream,garyrussell/spring-cloud-stream