Improve docs for Maria DB to include allowMultiQueries in JDBC

I followed the steps here: https://hasura.io/docs/latest/databases/mariadb/docker/

I was getting errors querying my data until I added `allowMultiQueries=true` param to my JDBC URL.

I suggest updating your docs so that the example is:

> **The JDBC connection URL should look like this:**
>
> `
> jdbc:mariadb://:/?user=&password=&allowMultiQueries=true
> `
>

More info: https://blog.jooq.org/mysqls-allowmultiqueries-flag-with-jdbc-and-jooq/