use jsonDeserializer object instead of new one.

app/src/main/java/org/javadev/kafkaexample/config/KafkaConsumerConfig.java

@@ -37,7 +37,7 @@ public class KafkaConsumerConfig {
         return new DefaultKafkaConsumerFactory<>(
                 consumerConfig(),
                 new StringDeserializer(),
-                new JsonDeserializer<>()
+                jsonDeserializer
         );
     }