fix new migration

superset/migrations/versions/2024-05-10_18-02_f84fde59123a_update_charts_with_old_time_comparison.py

@@ -33,7 +33,7 @@
 from sqlalchemy import Column, Integer, or_, String, Text
 from sqlalchemy.ext.declarative import declarative_base
 
-from superset import db
+from superset.extensions import db
 from superset.migrations.shared.utils import paginated_update
 from superset.utils.date_parser import get_since_until