Bump org.apache.kafka:kafka-clients in /arms-demo/mock-server

Bumps org.apache.kafka:kafka-clients from 2.4.0 to 2.6.3.

---
updated-dependencies:
- dependency-name: org.apache.kafka:kafka-clients
  dependency-type: direct:production
...

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Author: dependabot[bot]

arms-demo/mock-server/pom.xml

@@ -114,7 +114,7 @@
         <dependency>
             <groupId>org.apache.kafka</groupId>
             <artifactId>kafka-clients</artifactId>
-            <version>2.4.0</version>
+            <version>2.6.3</version>
         </dependency>
         <dependency>
             <groupId>mysql</groupId>