Switch DB to MySQL

[joemaller]

The reasons for initially switching to MariaDB are largely moot now. Less friction with MySQL.

docker-wordpress-dev/boilerplate-tooling/docker-compose.yml

Lines 3 to 5 in 360b62c

	# Image from: https://hub.docker.com/_/mariadb
	db:
	image: &db_img mariadb:11.5

https://hub.docker.com/_/mysql