[bitnami/ghost] chore!: :arrow_up: :boom: Bump MySQL subchart to 12

BREAKING CHANGE

Signed-off-by: Javier J. Salmerón García javier.salmeron@broadcom.com

This PR bumps the MySQL subchart to version 12.x.x, in order to continue having automated updates without issues.

[ ] Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
[ ] Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
[ ] Title of the pull request follows this pattern [bitnami/] Descriptive title
[ ] All commits signed off and in agreement of Developer Certificate of Origin (DCO)

bitnami / charts