Update Link for Istio

The URL for the ISTIO documentation has been updated from https://istio.io/docs/concepts/what-is-istio/ to https://istio.io/latest/about/service-mesh/#what-is-istio.
Please use the new URL to access the latest information on ISTIO documentation.

Signed-off-by: ydFu <[email protected]>

Author: ydFu

content/en/docs/reference/glossary/istio.md

@@ -2,7 +2,7 @@
 title: Istio
 id: istio
 date: 2018-04-12
-full_link: https://istio.io/docs/concepts/what-is-istio/
+full_link: https://istio.io/latest/about/service-mesh/#what-is-istio
 short_description: >
   An open platform (not Kubernetes-specific) that provides a uniform way to integrate microservices, manage traffic flow, enforce policies, and aggregate telemetry data.
 
@@ -17,4 +17,3 @@ tags:
 <!--more--> 
 
 Adding Istio does not require changing application code. It is a layer of infrastructure between a service and the network, which when combined with service deployments, is commonly referred to as a service mesh. Istio's control plane abstracts away the underlying cluster management platform, which may be Kubernetes, Mesosphere, etc.
-