Update kube-prom-stack chart to 15.4.2

flux/oas/prometheus-stack_hr.yaml

@@ -8,10 +8,12 @@ metadata:
     flux.weave.works/automated: "false"
 spec:
   releaseName: prometheus-stack
+  # https://github.com/prometheus-community/helm-charts/blob/main/charts/kube-prometheus-stack/Chart.yaml
+  # https://artifacthub.io/packages/helm/prometheus-community/kube-prometheus-stack
   chart:
     repository: https://prometheus-community.github.io/helm-charts
     name: kube-prometheus-stack
-    version: 14.5.0
+    version: 15.4.2
   valuesFrom:
     - secretKeyRef:
         name: prometheus-stack-settings