Update Docker Compose file format: 2.0 → 2.4 (minor)

[AndrewKvalheim]

Checklist

• I have read the Contribution & Best practices Guide.
• My branch is up-to-date with the upstream master branch.
• The tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works (if appropriate).
• I have added necessary documentation (if appropriate).

Short description of what this resolves

In my local development environment I'd like to limit resource usage, by setting in docker-compose.override.yml e.g.:

services:
  osem:
    cpus: 2
    mem_limit: 2gb

The cpus parameter requires Compose file version ~> 2.2, but the provided files are currently using 2.0.

Changes proposed in this pull request

Update to the latest version 2 format.