chore(deps): update container image kube-prometheus-stack to v56.21.0@fb857f3 by renovate (#18875)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[kube-prometheus-stack](https://togithub.com/prometheus-operator/kube-prometheus)
([source](https://togithub.com/prometheus-community/helm-charts)) |
minor | `56.9.0` -> `56.21.0` |

---

> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency
Dashboard for more information.

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This PR has been generated by [Renovate
Bot](https://togithub.com/renovatebot/renovate).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy4yMjUuMCIsInVwZGF0ZWRJblZlciI6IjM3LjIyNy4wIiwidGFyZ2V0QnJhbmNoIjoibWFzdGVyIn0=-->

charts/enterprise/prometheus/Chart.yaml

@@ -17,7 +17,7 @@ dependencies:
     tags: []
     import-values: []
   - name: kube-prometheus-stack
-    version: 56.9.0
+    version: 56.21.0
     repository: oci://ghcr.io/prometheus-community/charts
     condition: ""
     alias: kps

charts/operators/prometheus-operator/Chart.yaml

@@ -17,7 +17,7 @@ dependencies:
     tags: []
     import-values: []
   - name: kube-prometheus-stack
-    version: 56.9.0
+    version: 56.21.0
     repository: oci://ghcr.io/prometheus-community/charts
     condition: ""
     alias: kps
@@ -42,4 +42,4 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/operators/prometheus-operator
   - https://github.com/truecharts/containers/tree/master/apps/alpine
 type: application
-version: 6.3.0
+version: 6.4.0