PostDelete hook aren't applied on existing applications

[baurmatt]

Checklist:

• I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• I've included steps to reproduce the bug.
• I've pasted the output of argocd version.

Describe the bug

When an existing application get's updated with a resource that contains argocd.argoproj.io/hook: PostDelete it doesn't get the post-delete-finalizer.argocd.argoproj.io/post-delete-finalizer.argocd.argoproj.io/cleanup finalizers required for the PostDeletion feature to work.

To Reproduce

• Deploy a application without PostDelete hook
• Update the source of the application to include a new resource having the PostDelete hook annotation
• Sync the application
• Delete the application
  ==> See how the PostDelete hook isn't triggered

Expected behavior

PostDelete hook is triggered.

Screenshots

Version

argocd: v2.10.0+2175939
  BuildDate: 2024-02-06T14:28:43Z
  GitCommit: 2175939ed6156ddd743e60f427f7f48118c971bf
  GitTreeState: clean
  GoVersion: go1.21.3
  Compiler: gc
  Platform: linux/amd64

Logs

Paste any relevant application logs here.

[baurmatt]

Related to #16595

[baurmatt]

Sync vs Refresh. My bad :(