salt: Re-render kube-prometheus-stack Salt formula

Version of the chart has been bump to 15.4.4, so
we need to regenerate this formula as follows:

```
./charts/render.py prometheus-operator \
  charts/kube-prometheus-stack.yaml \
  charts/kube-prometheus-stack/ \
  --namespace metalk8s-monitoring \
  --service-config grafana \
  metalk8s-grafana-config \
  metalk8s/addons/prometheus-operator/config/grafana.yaml \
  metalk8s-monitoring \
  --service-config prometheus \
  metalk8s-prometheus-config \
  metalk8s/addons/prometheus-operator/config/prometheus.yaml \
  metalk8s-monitoring \
  --service-config alertmanager \
  metalk8s-alertmanager-config \
  metalk8s/addons/prometheus-operator/config/alertmanager.yaml \
  metalk8s-monitoring \
  --service-config dex \
  metalk8s-dex-config \
  metalk8s/addons/dex/config/dex.yaml.j2 metalk8s-auth \
  --drop-prometheus-rules charts/drop-prometheus-rules.yaml \
  > salt/metalk8s/addons/prometheus-operator/deployed/chart.sls
```

Refs: #3279