proposals/distribution: remove non-sense about image indexes

Signed-off-by: Stephen J Day <stephen.day@docker.com>

proposals/distribution.md

@@ -105,17 +105,15 @@ The following entries should be added to the [scope table][scope]:
 
     Tag-listing (e.g. “what named manifests are in `library/busybox`?”) endpoints are in scope and required for backwards compatibility with clients.
     External methods for listing tags remain compatible through fetching by content address, but are out of scope.
+    An endpoint for listing image repository names within a registry is considered out of scope for this specification.
 
     Managing the grouping of image repository names is considered part of distribution policy or content management, which are out of scope.
     For example, “which image repositories are under `library/`?” is out of scope for this project.
 
     * What: Specifying a distribution method
     * In/Out/Future: In scope
     * Status: In progress (see opencontainers/distribution-spec)
-    * Description: Define a protocol for creating, retrieving, updating, and deleting objects defined in the [image specification][image-spec].
-        Listing repositories (like [`/v2/_catalog`][catalog]) is a multi-[image-index][] action, which is out of scope for this entry.
-        Managing groups of image indexes requires multi-[image-index][] actions, which are out of scope for this entry.
-        Listing image indexes within a group is a multi-[image-index][] action, which is out of scope for this entry.
+    * Description: Define a protocol for creating, retrieving, updating, and deleting content-addressable objects, such as those defined in the [image specification][image-spec].
     * Why: This specification will provide one (of possibly many) distribution specifications.
         Alternative distribution specifications may be developed for uses cases not covered by this specification, but defining them is currently out of scope for the OCI.