Bump image in the CI-Template Jobs/Build.gitlab-ci.yml to 0.6.0

What does this MR do?

This MR sets the version of the image registry.gitlab.com/gitlab-org/cluster-integration/auto-build-image used in the CI template Jobs/Build.gitlab-ci.yml from 0.4.0 to 0.6.0.

Manual testing

@hfyngvason ran a couple of builds with the same overrides as present in this MR, and ran two build jobs:

1. on a Kubernetes runner: https://gitlab.com/hfyngvason/minimal-ruby-app/-/jobs/1257798712
2. on a shared runner: https://gitlab.com/hfyngvason/minimal-ruby-app/-/jobs/1257835500

Both succeeded.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because according to the guide, a CI template change doesn't require it. (Edit: This component includes new user facing features, so we include a changelog)
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content