Use RabbitMQ 4.0 in documentation

Author: acogoluegnes

README.adoc

@@ -76,7 +76,7 @@ Launch the broker:
 ----
 docker run -it --rm --name rabbitmq -p 5552:5552 -p 5672:5672 \
     -e RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS='-rabbitmq_stream advertised_host localhost' \
-    rabbitmq:3.13
+    rabbitmq:4.0
 ----
 
 Enable the stream plugin:

pom.xml

@@ -79,7 +79,7 @@
     <spotbugs-maven-plugin.version>4.8.6.3</spotbugs-maven-plugin.version>
     <spotbugs.version>4.8.6</spotbugs.version>
     <!-- for documentation -->
-    <broker.version>3.12</broker.version>
+    <broker.version>4.0</broker.version>
     <!-- to sign artifacts when releasing -->
     <gpg.keyname>6026DFCA</gpg.keyname>
     <maven.build.timestamp.format>yyyy-MM-dd'T'HH:mm:ss'Z'</maven.build.timestamp.format>