Bump mysql-connector-java in /frameworks/Java/spark

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.18 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/8.0.18...8.0.28)

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

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

frameworks/Java/spark/pom.xml

@@ -15,7 +15,7 @@
         <spark-version>2.9.0</spark-version>
         <hibernate-version>5.4.24.Final</hibernate-version>
         <gson-version>2.8.9</gson-version>
-        <mysql-connector-version>8.0.18</mysql-connector-version>
+        <mysql-connector-version>8.0.28</mysql-connector-version>
         <slf4j-version>1.7.25</slf4j-version>
         <exec.mainClass>hello.web.SparkApplication</exec.mainClass>
     </properties>