Describe the bug

Related resources with source in kcp currently get a "syncagent.kcp.io/cleanup" finalizer to prevent orphaned objects in the service provider cluster. This finalizer is not managed and will not get removed when the synced CR gets deleted. This requires manual cleanup interactions.
Possible related to #114 but the issue seems to be the other way around.

Steps To Reproduce

1. create a ConfigMap in a kcp workspace
2. create a synced CR referencing this ConfigMap
3. Wait for API-SyncAgent in the service provider cluster to add its finalizer on the ConfigMap
4. remove the CR created in step 2
5. list the finalizers on the ConfigMap

Expected Behaviour

I would expect the API-SyncAgent to remove its finalizer from the list as soon as the resource in the service provider cluster is deleted successfully.

Additional Context

No response