Update Istio to 1.6.8

Author: github-actions[bot]

istio/operator/manifests.yaml

@@ -15,7 +15,8 @@ metadata:
   namespace: istio-operator
   name: istio-operator
 ---
-# Source: istio-operator/templates/crd.yaml
+# Source: istio-operator/templates/crd-operator.yaml
+# SYNC WITH manifests/charts/base/files
 apiVersion: apiextensions.k8s.io/v1beta1
 kind: CustomResourceDefinition
 metadata:
@@ -224,7 +225,7 @@ spec:
       serviceAccountName: istio-operator
       containers:
         - name: istio-operator
-          image: docker.io/istio/operator:1.5.3
+          image: docker.io/istio/operator:1.6.8
           command:
           - operator
           - server