Pre-release images should use nightly cli

[nervetattoo]

Motivation for this request right now was that the CLI prompts (warn type message) to upgrade the migration file format, but the container is unable to run those migrations because it has the stable CLI which doesn't support the new file format.

This makes it hard to fully test upcoming releases. In my case I tried to use 5.0-beta.2 in staging to get as much testing time as possible to swiftly move to 5.0 in production.