[TEP-0079] Ownership and Maintenance

This commit updates the "Ownership and Maintenance" section of TEP-0079, reflecting recent changes in:

- [TEP-0110][tep-0110]: Decouple Tekton Catalog Organization
from Resource Reference
- [TEP-0115][tep-0115]: Tekton Catalog Git-Based Versioning
- tektoncd/hub#667: Migration from Tekton Hub to Artifact Hub

This commit also renames the "official" support tier to "verified" to avoid naming confusion with the [official status][official-status] in Artifact Hub

/kind tep

[tep-0079]: https://github.com/tektoncd/community/blob/main/teps/0079-tekton-catalog-support-tiers.md
[tep-0110]: https://github.com/tektoncd/community/blob/main/teps/0110-decouple-catalog-organization-and-reference.md
[tep-0115]: https://github.com/tektoncd/community/blob/main/teps/0115-tekton-catalog-git-based-versioning.md
[official-status]: https://artifacthub.io/docs/topics/repositories/#official-status