Bump mysql:mysql-connector-java in /arms-demo/mock-server

Bumps [mysql:mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 5.1.49 to 8.0.28.
- [Changelog](https://github.com/mysql/mysql-connector-j/blob/release/8.x/CHANGES)
- [Commits](mysql/mysql-connector-j@5.1.49...8.0.28)

---
updated-dependencies:
- dependency-name: mysql:mysql-connector-java
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

arms-demo/mock-server/pom.xml

@@ -119,7 +119,7 @@
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
-            <version>5.1.49</version>
+            <version>8.0.28</version>
         </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>