extra-thorough test for latest migration (#6567)

* extra-thorough test for latest migration

* one more comment

* make sure all "to_delete" vertexes are deleted

* use assert_equal instead of compare

Author: ajtmccarty

backend/infrahub/core/migrations/graph/m029_duplicates_cleanup.py

@@ -554,7 +554,7 @@ class PerformHardDeletes(Query):
     async def query_init(self, db: InfrahubDatabase, **kwargs: dict[str, Any]) -> None:  # noqa: ARG002
         query = """
 CALL {
-    MATCH (n:Node)
+    MATCH (n)
     WHERE n.to_delete = TRUE
     DETACH DELETE n
 }