Update the Windows node image 1809 version to 0709

cluster/gce/util.sh

@@ -2042,7 +2042,7 @@ function create-node-template() {
   elif [[ "${os}" == 'windows' ]]; then
       # TODO(pjh): revert back to using WINDOWS_NODE_IMAGE_FAMILY instead of
       # pinning to the v20190312 image once #76666 is resolved.
-      node_image_flags="--image-project ${WINDOWS_NODE_IMAGE_PROJECT} --image=windows-server-1809-dc-core-for-containers-v20190312"
+      node_image_flags="--image-project ${WINDOWS_NODE_IMAGE_PROJECT} --image=windows-server-1809-dc-core-for-containers-v20190709"
   else
       echo "Unknown OS ${os}" >&2
       exit 1