fix: real hash of HealthcheckItem

- it turns out that id() is not truly unique

src/daq/jobs/healthcheck.py

@@ -157,7 +157,7 @@ def handle_checks(self):
 
         # Alert if it's new
         for item, should_alert in res:
-            item_id = id(item.to_json())
+            item_id = hash(item.to_json())
             if should_alert and item_id not in self._sent_alert_items:
                 self._sent_alert_items.add(item_id)
                 self.send_alert(item)