message: docs: fix links to internal sections
diff: @@ -45,7 +45,7 @@ can be specified independently for each xDS API, pointing at an upstream
  cluster corresponding to a management server. This will initiate an
  independent bidirectional gRPC stream for each xDS resource type,
  potentially to distinct management servers. API delivery is eventually
  -consistent. See <Aggregated Discovery Service>`
  +consistent. See :ref:`Aggregated Discovery Service <xds_protocol_ads>`
  below for situations in which explicit control of sequencing is required.
  Type URLs
  @@ -188,7 +188,7 @@ resources. :ref:`resource_names <envoy_api_field_DiscoveryRequest.resource_names
  any superfluous resources. When a requested resource is missing in a RDS
  or EDS update, Envoy will retain the last known value for this resource
  except in the case where the `Cluster` or `Listener` is being
  -warmed. See <Resource Warming> section below on
  +warmed. See :ref:`Resource Warming <xds_protocol_resource_warming>` section below on
  the expectations during warming. The management server may be able to
  infer all the required EDS/RDS resources from the :ref:`node <envoy_api_msg_Core.Node>`
  identification in the :ref:`DiscoveryRequest <envoy_api_msg_DiscoveryRequest>`, in which case this hint may
  