STAC West - CMIP6 extension schema url points to local docker address

[bstrdsmkr]

The custom CMIP6 extension used by the West implementation is currently pointing to a local docker address (http://host.docker.internal/cmip6/v2.0.1/schema.json) which makes it unreachable publicly.

$ curl -s https://api.stac.esgf.ceda.ac.uk/collections/CMIP6/items | jq '.features[0].stac_extensions'
[
  "http://host.docker.internal/cmip6/v2.0.1/schema.json",
  "https://stac-extensions.github.io/alternate-assets/v1.2.0/schema.json",
  "https://stac-extensions.github.io/file/v2.1.0/schema.json"
]

Without a publicly reachable address, clients and test suites can't verify the schema