Equalize all host templates for Cognitive Language

To avoid validation errors seen in https://github.com/Azure/azure-rest-api-specs/pull/21068#issuecomment-1278304921, we should make sure all host templates are `{Endpoint}/language` despite having to repeat "/authoring/..." for each endpoint in _*-authoring.json_ swaggers.

I've also opened https://github.com/Azure/azure-sdk-tools/issues/4419 to fix the validation tools, but given how we decided that separate clients within an SDK should have separate directories, it's unlikely this will be fixed.

/cc @peytonfraser