Bump mysql-connector-java from 8.0.20 to 8.0.28 in /cpo-jdbc (#71)

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.20 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@8.0.20...8.0.28)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

cpo-jdbc/pom.xml

@@ -38,7 +38,7 @@
   </description>
   <properties>
     <oracleVersion>19.3.0.0</oracleVersion>
-    <mysqlVersion>8.0.20</mysqlVersion>
+    <mysqlVersion>8.0.28</mysqlVersion>
     <mariadbVersion>2.6.0</mariadbVersion>
     <h2Version>1.4.200</h2Version>
     <postgresVersion>42.4.1</postgresVersion>