update ExternalDNS to v0.13.6

Author: linki

cluster/manifests/external-dns/deployment.yaml

@@ -32,7 +32,7 @@ spec:
       serviceAccountName: external-dns
       containers:
       - name: external-dns
-        image: container-registry.zalando.net/teapot/external-dns:v0.13.5-master-37
+        image: container-registry.zalando.net/teapot/external-dns:v0.13.6-master-38
         args:
         - --source=service
         - --source=ingress