Fix unused imports (ruff lint)

Author: claude

tests/test_object.py

@@ -18,7 +18,7 @@
 import pytest
 
 import datajoint as dj
-from datajoint.objectref import ObjectRef, IntegrityError
+from datajoint.objectref import ObjectRef
 from datajoint.storage import build_object_path, generate_token, encode_pk_value
 
 from .schema_object import ObjectFile, ObjectFolder, ObjectMultiple, ObjectWithOther