Provisioner ignores SYMFONY__ENV__DATABASE_CHARSET

Wallabag is configured like this in docker-compose.yml:

```
wallabag:
image: wallabag/wallabag:2.3.0
environment:
MYSQL_ROOT_PASSWORD:
SYMFONY__ENV__DATABASE_DRIVER: pdo_mysql
SYMFONY__ENV__DATABASE_HOST: mariadb
SYMFONY__ENV__DATABASE_PORT: 3306
SYMFONY__ENV__DATABASE_NAME: wallabag
SYMFONY__ENV__DATABASE_USER: wallabag
SYMFONY__ENV__DATABASE_PASSWORD:
SYMFONY__ENV__DATABASE_CHARSET: utf8mb4
SYMFONY__ENV__MAILER_HOST: smtp
SYMFONY__ENV__MAILER_USER: ""
SYMFONY__ENV__MAILER_PASSWORD: ""
SYMFONY__ENV__FROM_EMAIL:
SYMFONY__ENV__FOSUSER_REGISTRATION: "true"
SYMFONY__ENV__DOMAIN_NAME:
SYMFONY__ENV__SECRET:
restart: unless-stopped
links:
- redis:redis
expose:
- 80
depends_on:
- smtp
- redis
- mariadb
- nginx
```

No matter what I do, parameters.yml have utf8 as an charset instead of utf8mb4:

```
# docker exec -it dockerconfig_wallabag_1 grep database_charset /var/www/wallabag/app/config/parameters.yml
database_charset: utf8

```