fix: update version for action and Docker image

[bewuethr]

Pull Request

Proposed Changes

As discussed in #371, v6.0.0 of the action is still pulling the v5 Docker image, which has permission problems. In this PR, I'm updating the metadata file to fix that, and also update other references to the Docker image and the action itself to consistently use v6.

Readiness Checklist

Author/Contributor

• If documentation is needed for this change, has that been included in this pull request
• run make lint and fix any issues that you have introduced (didn't touch linted files)
• run make test and ensure you have test coverage for the lines you are introducing (didn't touch Python files)
• If publishing new data to the public (scorecards, security scan results, code quality results, live dashboards, etc.), please request review from @jeffrey-luszcz

Reviewer

• Label as either fix, documentation, enhancement, infrastructure, maintenance or breaking

cc @jmeridth