Bug with DiffSyncModelFlags.NATURAL_DELETION_ORDER

### Environment
* DiffSync version:  1.9.0

### Observed Behavior

When you have a parent with no changes that has a child with changes and are using `DiffSyncModelFlags.NATURAL_DELETION_ORDER` on the parent, the child will never be synced.

### Expected Behavior

The child should be synced.

### Steps to Reproduce

Check unit test in #249 