update prow rc image with 1.8.0-rc1 candidate

Author: songjiaxun

deploy/kubernetes/images/prow-stable-sidecar-rc-master/image.yaml

@@ -7,7 +7,7 @@ metadata:
   name: imagetag-csi-provisioner-prow-rc
 imageTag:
   name: k8s.gcr.io/sig-storage/csi-provisioner
-  newTag: "v3.1.1"
+  newTag: "v3.2.1"
 ---
 apiVersion: builtin
 kind: ImageTagTransformer
@@ -48,6 +48,6 @@ metadata:
 imageTag:
   name: k8s.gcr.io/cloud-provider-gcp/gcp-compute-persistent-disk-csi-driver
   newName: gcr.io/k8s-staging-cloud-provider-gcp/gcp-compute-persistent-disk-csi-driver
-  newTag: "v1.7.2-rc1"
+  newTag: "v1.8.0-rc1"
 ---