chore(ci): bump microk8s to 1.31

Ref canonical/bundle-kubeflow#1157

Author: orfeas-k

.github/workflows/integrate.yaml

@@ -67,7 +67,7 @@ jobs:
         uses: charmed-kubernetes/actions-operator@main
         with:
           provider: microk8s
-          channel: 1.29-strict/stable
+          channel: 1.31-strict/stable
           juju-channel: 3.6/stable
           charmcraft-channel: 3.x/stable