SpringBoot Fix MariaDB driver product name

Fix MariaDB driver product name issue : https://github.com/spring-projects/spring-boot/issues/25127

Comment From: snicoll

@anudeepg thank you for making your first contribution to Spring Boot.

This issue is noteworthy as a MariaDB backend previously returned a mysql platform id. With this change, the platform id is mariadb.

Those who are using this identifier, for instance for database initialization purposes, can adapt their scripts accordingly (or translate that back to mysql if need to be as the polish commit shows).