Update dependency io.confluent:kafka-avro-serializer to v7 (#21)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

pom.xml

@@ -98,7 +98,7 @@
         <dependency>
             <groupId>io.confluent</groupId>
             <artifactId>kafka-avro-serializer</artifactId>
-            <version>5.5.15</version>
+            <version>7.7.1</version>
             <scope>test</scope>
         </dependency>