chore(deps): Bump fluxcd/source-controller in /pkg/svc/installer/flux (#5306)

Bumps [fluxcd/source-controller](https://github.com/fluxcd/source-controller) from v1.8.5 to v1.9.0.
- [Release notes](https://github.com/fluxcd/source-controller/releases)
- [Changelog](https://github.com/fluxcd/source-controller/blob/main/CHANGELOG.md)
- [Commits](fluxcd/source-controller@v1.8.5...v1.9.0)

---
updated-dependencies:
- dependency-name: fluxcd/source-controller
  dependency-version: v1.9.0
  dependency-type: direct:production
...

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Author: dependabot[bot]

pkg/svc/installer/flux/Dockerfile.distribution

@@ -11,7 +11,7 @@
 # - ghcr.io/fluxcd/helm-controller → deployed by FluxInstance
 # - ghcr.io/fluxcd/notification-controller → deployed by FluxInstance
 
-FROM ghcr.io/fluxcd/source-controller:v1.8.5
+FROM ghcr.io/fluxcd/source-controller:v1.9.0
 FROM ghcr.io/fluxcd/kustomize-controller:v1.9.0
 FROM ghcr.io/fluxcd/helm-controller:v1.5.5
 FROM ghcr.io/fluxcd/notification-controller:v1.8.4