chore: Remove commented out Molecule platforms

[alessfg]

Proposed changes

Remove commented out Molecule platforms and GitHub Actions QEMU step for the time being. These changes will be reverted if multi-arch testing can be reinstated in GitHub Actions.

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• [x] I have read the CONTRIBUTING document.
• [x] I have added Molecule tests that prove my fix is effective or that my feature works.
• [x] I have checked that any relevant Molecule tests pass after adding my changes.
• [x] I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md).