chore(flux): update image app-template 3.7.2 → 3.7.3 (clustertool) (#33236)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [app-template](https://redirect.github.com/bjw-s/helm-charts) | patch
| `3.7.2` -> `3.7.3` |

---

### Release Notes

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

###
[`v3.7.3`](https://redirect.github.com/bjw-s/helm-charts/releases/tag/app-template-3.7.3)

[Compare
Source](https://redirect.github.com/bjw-s/helm-charts/compare/app-template-3.7.2...app-template-3.7.3)

#### Changelog:

##### Fixed

-   Fixed name suffix for HTTPRoute
-   Fixed incorrect default backendRefs values in HTTPRoute

</details>

---

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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: 3.7.2
+      version: 3.7.3
       sourceRef:
         kind: HelmRepository
         name: bjw-s