Bump mysql-connector-java from 8.0.16 to 8.0.28 in /demos/producer

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.16 to 8.0.28.
- [Release notes](https://github.com/mysql/mysql-connector-j/releases)
- [Changelog](https://github.com/mysql/mysql-connector-j/blob/release/8.0/CHANGES)
- [Commits](mysql/mysql-connector-j@8.0.16...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]

demos/producer/pom.xml

@@ -50,7 +50,7 @@
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
-            <version>8.0.16</version>
+            <version>8.0.28</version>
         </dependency>
         <dependency>
             <groupId>org.flywaydb</groupId>