docs: make external-dns example to 0.7.2+ working in AWS China (#1680)

Co-authored-by: M00nF1sh <[email protected]>

Author: zxkane

docs/examples/external-dns.yaml

@@ -22,7 +22,7 @@ rules:
   verbs: ["list"]
 - apiGroups: [""]
   resources: ["endpoints"]
-  verbs: ["get", "watch", "list"]
+  verbs: ["get","watch","list"]  
 ---
 apiVersion: rbac.authorization.k8s.io/v1beta1
 kind: ClusterRoleBinding
@@ -55,7 +55,11 @@ spec:
       serviceAccountName: external-dns
       containers:
       - name: external-dns
-        image: bitnami/external-dns:0.7.1
+        image: bitnami/external-dns:0.7.4
+        # must specify env AWS_REGION in AWS china regions
+        # env:
+        # - name: AWS_REGION
+        #   value: cn-north-1
         args:
         - --source=service
         - --source=ingress