chore(deps): update helm release kube-prometheus-stack to v81

Author: renovate[bot]

hack/distro/monitoring/kube-prometheus-stack/release.flux.yaml

@@ -13,7 +13,7 @@ spec:
   chart:
     spec:
       chart: kube-prometheus-stack
-      version: "80.14.4"
+      version: "81.2.2"
       sourceRef:
         kind: HelmRepository
         name: kube-prometheus-stack