GKE: Update K8s version to 1.31 (elastic#8588)

Author: barkbay

hack/deployer/config/plans.yml

@@ -3,7 +3,7 @@ plans:
   operation: create
   clusterName: ci
   provider: gke
-  kubernetesVersion: 1.30
+  kubernetesVersion: 1.31
   machineType: n1-standard-8
   serviceAccount: true
   enforceSecurityPolicies: true
@@ -18,7 +18,7 @@ plans:
   operation: create
   clusterName: ci-autopilot
   provider: gke
-  kubernetesVersion: 1.30
+  kubernetesVersion: 1.31
   serviceAccount: true
   enforceSecurityPolicies: true
   # this is disabled in autopilot: container provisioner is privileged; not allowed in Autopilot
@@ -31,7 +31,7 @@ plans:
   operation: create
   clusterName: dev
   provider: gke
-  kubernetesVersion: 1.30
+  kubernetesVersion: 1.31
   machineType: n1-standard-8
   serviceAccount: false
   enforceSecurityPolicies: true
@@ -58,7 +58,7 @@ plans:
   operation: create
   clusterName: dev-autopilot
   provider: gke
-  kubernetesVersion: 1.30
+  kubernetesVersion: 1.31
   serviceAccount: false
   enforceSecurityPolicies: true
   gke: