Merge pull request #8300 from jincong8973/master

feat: improve external gPRC ca example

Author: k8s-ci-robot

cluster-autoscaler/cloudprovider/externalgrpc/examples/certmanager-manifests/ca.yaml

@@ -7,6 +7,7 @@ spec:
   isCA: true
   commonName: selfsigned-ca
   secretName: ca-root-secret
+  duration: 87600h
   privateKey:
     algorithm: ECDSA
     size: 256