Update RC image for 1.2.0 RC

Author: saad-ali

deploy/kubernetes/images/prow-gke-release-staging-rc/image.yaml

@@ -32,7 +32,7 @@ metadata:
 imageTag:
   name: gke.gcr.io/gcp-compute-persistent-disk-csi-driver
   newName: gcr.io/gke-release-staging/gcp-compute-persistent-disk-csi-driver
-  newTag: "v1.1.0-rc1"
+  newTag: "v1.2.0-rc1"
 ---
 
 apiVersion: builtin