docs(OWNERS.md): Move vdice to the Emeritus section

[vdice]

What does this change

Moving to the Emeritus Maintainers section of OWNERS.md as I'm no longer an active maintainer of this project. ❤️

Notes for the reviewer

Ref #2728

Checklist

• Did you write tests?
• Did you write documentation?
• Did you change porter.yaml or a storage document record? Update the corresponding schema file.
• If this is your first pull request, please add your name to the bottom of our Contributors list. Thank you for making Porter better! 🙇‍♀️

Reviewer Checklist

• Comment with /azp run test-porter-release if a magefile or build script was modified
• Comment with /azp run porter-integration if it's a non-trivial PR

[carolynvs]

Thank you @vdice for your contributions to the project. I always enjoy working with you! Best of luck to you and if you ever feel like coming back, just say the word. ❤️