Prior to this change, the installation instructions directly use the resource urls in the Catalog repo, which results in tight coupling between the organization and how users fetch resources (as described in TEP-0110). This commit updates the installation guide to install Tekton Catalog resources via Tekton Hub Api: https://github.com/tektoncd/hub/pull/539
This change decouples the Tekton Catalog organization from resouces resolution, which enables Tekton Catalog reorganization.
