This was missing from [an earlier PR](https://github.com/apache/kafka/pull/2247) that escaped these symbols in another section of the doc.
Author: Vahid Hashemian <vahidhashemian@us.ibm.com>
Reviewers: Ewen Cheslack-Postava <ewen@confluent.io>
Closes#2453 from vahidhashemian/doc/escape_lt_gt_in_streams_code