Draft: Resolve "Repository Maintenance"

What is your Merge about?

This issue covers multiple maintenance items for this repository:

• Remove digest pinning in hardening_manifest.yaml.
• Update maintainers list.
• Remove renovate.json since it is no longer required.

Note: Please be sure you create an issue related to this merge request and the issue is labeled StatusReview, this will initiate a CHT member review of your merge request.