thrift proxy: minor api docs update for new trds feature (#20863)

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

Mirrored from https://github.com/envoyproxy/envoy @ 548d22e39258b5294a598f61e60aa0603e11c240

envoy/extensions/filters/network/thrift_proxy/v3/route.proto

@@ -24,7 +24,11 @@ message RouteConfiguration {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.filter.network.thrift_proxy.v2alpha1.RouteConfiguration";
 
-  // The name of the route configuration. Reserved for future use in asynchronous route discovery.
+  // The name of the route configuration. This name is used in asynchronous route discovery.
+  // For example, it might match
+  // :ref:`route_config_name
+  // <envoy_v3_api_field_extensions.filters.network.thrift_proxy.v3.Trds.route_config_name>` in
+  // :ref:`envoy_v3_api_msg_extensions.filters.network.thrift_proxy.v3.Trds`.
   string name = 1;
 
   // The list of routes that will be matched, in order, against incoming requests. The first route