I had some difficulties connecting to the devservices databases of a service with multiple datasources because the [documentation in the Dev Services for Databases guide](https://quarkus.io/guides/databases-dev-services#connect-to-database-run-as-a-dev-service) is wrong.

1. 1. 1. How to verify

Inspect the devservice database containers of a multi-datasource application with `docker inspect`.

Here are the env vars of the postgres container for the named datasource "db1":

```shell
$ docker container inspect unruffled_franklin --format 'json .Config.Env' | jq -r '.[]' | grep POSTGRES
POSTGRES_USER=quarkus
POSTGRES_PASSWORD=quarkus
POSTGRES_DB=db1
```

For reference, these are the corresponding env vars from a devservices container for the default database in a single-datasource setup:
```shell
$ docker container inspect clever_murdock --format 'json .Config.Env' | jq -r '.[]' | grep POSTGRES
POSTGRES_USER=quarkus
POSTGRES_PASSWORD=quarkus
POSTGRES_DB=quarkus
```

This PR fixes the issue.