FIX(image-updater): change write-back method to argocd

- Remove dependency on github-creds secret
- Use ArgoCD write-back instead of git

jovies/argocd.yaml

@@ -8,7 +8,7 @@ metadata:
   annotations:
     argocd-image-updater.argoproj.io/image-list: jovies=ghcr.io/mayne0213/jovies:latest
     argocd-image-updater.argoproj.io/jovies.update-strategy: digest
-    argocd-image-updater.argoproj.io/write-back-method: git:secret:argocd/github-creds
+    argocd-image-updater.argoproj.io/write-back-method: argocd
     argocd-image-updater.argoproj.io/git-branch: main
     argocd-image-updater.argoproj.io/jovies.helm.image-tag: image.tag
 spec: