Removed Avro topic from TOC on kafka
Removed TOC entry in Streams Developer Guide for Avro, since we have no content for this
PR on kafka-site: apache/kafka-site#195
Reviewers: Guozhang Wang
<li><a class="reference internal" href="#available-serdes" id="id3">Available SerDes</a></li>
<ul>
<li><a class="reference internal" href="#primitive-and-basic-types" id="id4">Primitive and basic types</a></li>
- <li><a class="reference internal" href="#avro" id="id5">Avro</a></li>
<li><a class="reference internal" href="#json" id="id6">JSON</a></li>
<li><a class="reference internal" href="#further-serdes" id="id7">Further serdes</a></li>
</ul>
