fix(image-automation): use .Changed in commit message template

ImageUpdateAutomation reported "template uses removed '.Updated'
field. Please use '.Changed' instead." Updating per the v1beta2
docs (https://fluxcd.io/flux/components/image/imageupdateautomations/#message-template).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

kubernetes/infrastructure/image-automation/update-automation.yaml

@@ -22,7 +22,7 @@ spec:
         email: security-bot@renner.uno
         name: Flux Image Automation
       messageTemplate: |
-        chore(image-automation): bump {{ range $image, $_ := .Updated.Images }}{{ $image }} {{ end }}
+        chore(image-automation): bump {{ range .Changed.Changes }}{{ .ImageRef }} {{ end }}
 
         Update by image-automation-controller from upstream tags.
     push: