test-infra: update microk8s

[bartoszmajsak]

What can be improved

We're locked on microk8s 1.19 and thus on istio-1.10 addon. With 1.24 addons are moved to their own repositories and istio is based on 1.14.x

Why

To be closer to the latest stable releases.

[bartoszmajsak]

Updating to 1.25 stable with istio 1.14.4 results in installation process timing out. Needs investigation.

- Processing resources for Ingress gateways. Waiting for Deployment/istio-system/istio-ingressgateway- Processing resources for Ingress gateways. Waiting for Deployment/istio-system/istio-ingressgateway✘ Ingress gateways encountered an error: failed to wait for resource: resources not ready after 5m0s: timed out waiting for the condition