Upgrade to MySQL 8.4.0 LTS

[jobmission]

MySQL 8.4.0 has been released as a long-term supported version.

See release.

[wilkinsona]

This is covered in the issue template:

• Managed Dependency Upgrade
  You DO NOT need to raise an issue for a managed dependency version upgrade as there's a semi-automatic process for checking managed dependencies for new versions before a release

We'll upgrade to 8.4 (or later) in Spring Boot 3.4. It's too late to do so in Spring Boot 3.3. In the meantime, you can use the mysql.version property to override the version if you wish.