chore(deps): update helm release kube-prometheus-stack to v55.8.1 (#304)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [kube-prometheus-stack](https://github.com/prometheus-operator/kube-prometheus) ([source](https://github.com/prometheus-community/helm-charts)) | minor | `55.7.1` -> `55.8.1` |

---

### Release Notes

<details>
<summary>prometheus-community/helm-charts (kube-prometheus-stack)</summary>

### [`v55.8.1`](https://github.com/prometheus-community/helm-charts/releases/tag/kube-prometheus-stack-55.8.1)

[Compare Source](prometheus-community/helm-charts@kube-prometheus-stack-55.8.0...kube-prometheus-stack-55.8.1)

kube-prometheus-stack collects Kubernetes manifests, Grafana dashboards, and Prometheus rules combined with documentation and scripts to provide easy to operate end-to-end Kubernetes cluster monitoring with Prometheus using the Prometheus Operator.

#### What's Changed

-   \[kube-prometheus-stack] Avoid nil pointer error with empty thanos config by [@&#8203;gracedo](https://github.com/gracedo) in prometheus-community/helm-charts#4132

**Full Changelog**: prometheus-community/helm-charts@kube-prometheus-stack-55.8.0...kube-prometheus-stack-55.8.1

### [`v55.8.0`](https://github.com/prometheus-community/helm-charts/releases/tag/kube-prometheus-stack-55.8.0)

[Compare Source](prometheus-community/helm-charts@kube-prometheus-stack-55.7.1...kube-prometheus-stack-55.8.0)

kube-prometheus-stack collects Kubernetes manifests, Grafana dashboards, and Prometheus rules combined with documentation and scripts to provide easy to operate end-to-end Kubernetes cluster monitoring with Prometheus using the Prometheus Operator.

#### What's Changed

-   \[kube-prometheus-stack] Bump chart dependencies by [@&#8203;dotdc](https://github.com/dotdc) in prometheus-community/helm-charts#4141

**Full Changelog**: prometheus-community/helm-charts@kube-state-metrics-5.16.0...kube-prometheus-stack-55.8.0

</details>

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Reviewed-on: https://git.home/nrdufour/home-ops/pulls/304
Co-authored-by: Renovate <[email protected]>
Co-committed-by: Renovate <[email protected]>

kubernetes/main/apps/observability/kube-prometheus-stack/app/helm-release.yaml

@@ -10,7 +10,7 @@ spec:
   chart:
     spec:
       chart: kube-prometheus-stack
-      version: 55.7.1
+      version: 55.8.1
       sourceRef:
         kind: HelmRepository
         name: prometheus-community-charts