Fix ociReference formatting in collection-index.yml

[AntonZheng]

What type of PR is this?

• Add a new dev container collection
• Update to an existing dev container collection
• Documentation/spec update
• Other containers.dev site update (UX, layout, etc)

Description

following previous pr: #607

While the collection was showing up in https://containers.dev/collections I don't see the template showing up https://containers.dev/templates

Think this could be because we reference the template itself instead of the collection as the oci reference. PR is to update to point to the collection itself.

[AntonZheng]

@AlvaroRausell thanks for your previous review! After the check in the collection was showing up in https://containers.dev/collections

However I noticed that the template didn't seem to show up in the templates page https://containers.dev/templates. Noticed that the oci reference was referencing the actual template instead of the collection. Could this fix the issue?

link to repo with packages:
https://github.com/Azure/edgeactions-devcontainers

Appreciate the help!