cli/trust: remove special handling for "plugin" Class

This code depended on the registry Service interface, which has been removed,
so needed to be refactored. Digging further into the reason this code existed,
it looked like the Class=plugin was previously required on Docker Hub to handle
plugins, but this requirement is no longer there, so we can remove this special
handling.

This patch removes the special handling to both remove the use of the registry.Service
interface, as well as removing complexity that is no longer needed.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/container/create.go

@@ -227,7 +227,7 @@ func createContainer(ctx context.Context, dockerCli command.Cli, containerConfig
 
 		if taggedRef, ok := namedRef.(reference.NamedTagged); ok && !opts.untrusted {
 			var err error
-			trustedRef, err = image.TrustedReference(ctx, dockerCli, taggedRef, nil)
+			trustedRef, err = image.TrustedReference(ctx, dockerCli, taggedRef)
 			if err != nil {
 				return nil, err
 			}