Pinning Docker Compose version for Travis in order to avoid intermittent Docker errors

[caiosba]

Description

We've been facing different errors in Alegre Travis jobs related to Docker, for example:

The Compose file './docker-compose.yml' is invalid because:
Unsupported config option for services.alegre: 'platform'
Unsupported config option for services.postgres: 'platform'
Unsupported config option for services.queue_worker: 'platform'

And:

Service 'postgres' failed to build: missing signature key

It doesn't happen consistently. Although the Travis file is configured for dist: jammy (which is the latest they support), looks like different versions of Docker are used in different jobs.

For now, my suggestion to fix this is by using a pinned version of the latest Docker Compose version. Once we move from Travis to GitHub Actions hopefully this can be more stable and use the latest versions of these packages.

(No ticket created for this).

How has this been tested?

The Travis job passed after these changes: https://app.travis-ci.com/github/meedan/alegre/builds/272951439