Newt keeps performing healthchecks after Public resource is deleted

### Describe the Bug

Not sure if this one is Newt or Pangolin though likely Pangolin should instruct Newt not to ping the public resource. Anyways, I noticed Newt keeps performing healthchecks for the resource, which was already deleted hours ago. Newt stops healthchecks after the restart.

### Environment

- OS Type & Version: Fedora 43
- Pangolin Version: 1.16.2
- Gerbil Version: 1.3.0
- Traefik Version: 3.6.10
- Newt Version: 1.10.2

### To Reproduce

* configure healthcheck for a public resource
* check newt log to see healthcheck works
* remove the public resource - healthchecks will continue

### Expected Behavior

Healthcheck must stop after deleting the public resource