docs: Fix auto-host-rewrite doc (#29888)

* Fix auto-host-rewrite doc

auto-host-rewrite does have effect when using EDS and setting hostname
field.

Signed-off-by: Jihoon Chung <jihoon@gmail.com>

* kick ci

Signed-off-by: Jihoon Chung <jihoon@gmail.com>

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Signed-off-by: Jihoon Chung <jihoon@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 8399fb4c7ef2ab4e8350db63e561e6cc54ac5144

envoy/config/route/v3/route_components.proto

@@ -1139,7 +1139,9 @@ message RouteAction {
     // Indicates that during forwarding, the host header will be swapped with
     // the hostname of the upstream host chosen by the cluster manager. This
     // option is applicable only when the destination cluster for a route is of
-    // type ``strict_dns`` or ``logical_dns``. Setting this to true with other cluster types
+    // type ``strict_dns`` or ``logical_dns``,
+    // or when :ref:`hostname <envoy_v3_api_field_config.endpoint.v3.Endpoint.hostname>`
+    // field is not empty. Setting this to true with other cluster types
     // has no effect. Using this option will append the
     // :ref:`config_http_conn_man_headers_x-forwarded-host` header if
     // :ref:`append_x_forwarded_host <envoy_v3_api_field_config.route.v3.RouteAction.append_x_forwarded_host>`