docs: update doc for ReferrerListPageSize (#842)

Resolves: #841
Signed-off-by: Lixia (Sylvia) Lei <[email protected]>

registry/remote/repository.go

@@ -118,7 +118,12 @@ type Repository struct {
 	// ReferrerListPageSize specifies the page size when invoking the Referrers
 	// API.
 	// If zero, the page size is determined by the remote registry.
-	// Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0/spec.md#listing-referrers
+	//
+	// NOTE: Pagination for the Referrers API is not defined in the distribution
+	// spec, so not all registries support it. ReferrerListPageSize may be
+	// ignored if pagination is unsupported by the remote registry.
+	//
+	// Reference: https://github.com/oras-project/oras-go/issues/841
 	ReferrerListPageSize int
 
 	// MaxMetadataBytes specifies a limit on how many response bytes are allowed