util.sh: Replace wait-until-stable with wait-until --stable

This change follows the recommendation from the CI logs:

"WARNING: `gcloud compute instance-groups managed wait-until-stable` is
deprecated. Please use `gcloud compute instance-groups managed
wait-until --stable` instead."

Signed-off-by: Joakim Roubert <[email protected]>

Author: joakimr-axis

cluster/gce/util.sh

@@ -3033,7 +3033,7 @@ function create-linux-nodes() {
           --base-instance-name "${extra_group_name}" \
           --size "${num_additional}" \
           --template "${extra_template_name}" || true;
-      gcloud compute instance-groups managed wait-until-stable \
+      gcloud compute instance-groups managed wait-until --stable \
           "${extra_group_name}" \
           --zone "${ZONE}" \
           --project "${PROJECT}" \
@@ -3064,7 +3064,7 @@ function create-linux-nodes() {
           --base-instance-name "${group_name}" \
           --size "${this_mig_size}" \
           --template "${template_name}" || true;
-      gcloud compute instance-groups managed wait-until-stable \
+      gcloud compute instance-groups managed wait-until --stable \
           "${group_name}" \
           --zone "${ZONE}" \
           --project "${PROJECT}" \
@@ -3104,7 +3104,7 @@ function create-windows-nodes() {
         --base-instance-name "${group_name}" \
         --size "${this_mig_size}" \
         --template "${template_name}" || true;
-    gcloud compute instance-groups managed wait-until-stable \
+    gcloud compute instance-groups managed wait-until --stable \
         "${group_name}" \
         --zone "${ZONE}" \
         --project "${PROJECT}" \