Merge branch 'renovate/kube-prometheus-stack-21.x' into 'main'

Update Helm release kube-prometheus-stack to v21

See merge request stackspin/stackspin!643

flux2/apps/monitoring/kube-prometheus-stack-release.yaml

@@ -11,7 +11,7 @@ spec:
       # https://artifacthub.io/packages/helm/prometheus-community/kube-prometheus-stack
       # renovate: registryUrl=https://prometheus-community.github.io/helm-charts
       chart: kube-prometheus-stack
-      version: 20.0.1
+      version: 21.0.0
       sourceRef:
         kind: HelmRepository
         name: prometheus-community