Bump org.apache.activemq:activemq-broker (#2606)

Bumps [org.apache.activemq:activemq-broker](https://github.com/apache/activemq) from 6.2.0 to 6.2.4.
- [Release notes](https://github.com/apache/activemq/releases)
- [Commits](apache/activemq@activemq-6.2.0...activemq-6.2.4)

---
updated-dependencies:
- dependency-name: org.apache.activemq:activemq-broker
  dependency-version: 6.2.4
  dependency-type: direct:development
...

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examples/activemq-multiple-brokers/pom.xml

@@ -141,7 +141,7 @@
     <dependency>
       <groupId>org.apache.activemq</groupId>
       <artifactId>activemq-broker</artifactId>
-      <version>6.2.0</version>
+      <version>6.2.4</version>
       <scope>test</scope>
     </dependency>
   </dependencies>