Update confluentinc/ksqldb-examples Docker tag to v7.3.0

Author: renovate[bot]

docker/docker-compose.kafkacluster.yml

@@ -129,7 +129,7 @@ services:
       PORT: 9021
 
   ksql-datagen:
-    image: confluentinc/ksqldb-examples:7.1.0
+    image: confluentinc/ksqldb-examples:7.3.0
     hostname: ksql-datagen
     container_name: ksql-datagen
     depends_on: