Bump mysql-connector-java in /sparkjava-mysql/backend

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.11 to 8.0.16.
- [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/8.0.11...8.0.16)

Signed-off-by: dependabot[bot] <support@github.com>

sparkjava-mysql/backend/pom.xml

@@ -46,7 +46,7 @@
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
-            <version>8.0.11</version>
+            <version>8.0.16</version>
         </dependency>
         <dependency>
             <groupId>com.google.code.gson</groupId>