build(deps-dev): bump mysql-connector-java in /examples/JDBC/taosdemo (#16097)

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](https://github.com/mysql/mysql-connector-j/compare/8.0.16...8.0.28)

---
updated-dependencies:
- dependency-name: mysql:mysql-connector-java
  dependency-type: direct:development
...
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examples/JDBC/taosdemo/pom.xml

@@ -81,7 +81,7 @@
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
-            <version>8.0.16</version>
+            <version>8.0.28</version>
             <scope>test</scope>
         </dependency>
         <!-- log4j -->