Apply Black formatting to assign_object.py to green ci-lint (#7154)

Add the trailing comma Black (the version ci-lint pins) expects on the
create_entity kwargs, so lint-formatting passes on this PR. Formatting only,
no behaviour change.

Generated with the assistance of an AI coding tool.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ifcopenshell-python/ifcopenshell/api/aggregate/assign_object.py

@@ -161,7 +161,7 @@ def assign_object(
                 "OwnerHistory": ifcopenshell.api.owner.create_owner_history(file),
                 "RelatedObjects": list(products_set),
                 "RelatingObject": relating_object,
-            }
+            },
         )
 
     # localize placement relative to a new aggregate for affected products