chore(flux): update image app-template 4.1.2 → 4.2.0 (clustertool) (#37876)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [app-template](https://redirect.github.com/bjw-s-labs/helm-charts) |
minor | `4.1.2` -> `4.2.0` |

---

### Release Notes

<details>
<summary>bjw-s-labs/helm-charts (app-template)</summary>

###
[`v4.2.0`](https://redirect.github.com/bjw-s-labs/helm-charts/releases/tag/app-template-4.2.0)

[Compare
Source](https://redirect.github.com/bjw-s-labs/helm-charts/compare/app-template-4.1.2...app-template-4.2.0)

#### Changelog:

##### Changed

- Upgraded the common library to v4.2.0
- [Upgrade
notes](https://bjw-s-labs.github.io/helm-charts/docs/app-template/upgrade-instructions/)
- [Detailed release
notes](https://redirect.github.com/bjw-s-labs/helm-charts/releases/tag/common-4.2.0)

</details>

---

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---

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clustertool/embed/generic/kubernetes/system/system-upgrade-controller/app/helm-release.yaml

@@ -10,7 +10,7 @@ spec:
   chart:
     spec:
       chart: app-template
-      version: 4.1.2
+      version: 4.2.0
       sourceRef:
         kind: HelmRepository
         name: bjw-s