:gear: slightly easier docker config

docker-compose.yml

         environment:
             MYSQL_ROOT_PASSWORD: "${DB_PASSWORD}"
             INNODB_FLUSH_METHOD: O_DSYNC
-            MYSQL_USER: "${WORDPRESS_DB_USER}"
-            MYSQL_PASSWORD: "${WORDPRESS_DB_PASSWORD}"
             MYSQL_DATABASE: "${DB_NAME}"
         volumes:
             - db:/var/lib/mysql