Update sample readme to public preview (#10)

avro/samples/README.md

@@ -1,4 +1,4 @@
-## [Private Preview] Kafka Avro Integration for Azure Schema Registry
+## [Public Preview] Kafka Avro Integration for Azure Schema Registry
 This document will show how to run Kafka-integrated Apache Avro serializers and deserializers backed by Azure Schema Registry
 
 ## Prerequisites
@@ -44,4 +44,4 @@ The generated class can be found in the `target/generated-sources` folder.
 The code can then be run with the follow command:
 ```bash
 mvn -e clean compile exec:java -Dexec.mainClass="com.azure.schemaregistry.samples.App"
-```
+```