fix: Rename on_delete parameter to ondelete (apache#25424)

Author: john-bodley

superset/models/dashboard.py

@@ -130,13 +130,13 @@ def copy_dashboard(_mapper: Mapper, connection: Connection, target: Dashboard) -
     Column(
         "dashboard_id",
         Integer,
-        ForeignKey("dashboards.id", on_delete="CASCADE"),
+        ForeignKey("dashboards.id", ondelete="CASCADE"),
         nullable=False,
     ),
     Column(
         "role_id",
         Integer,
-        ForeignKey("ab_role.id", on_delete="CASCADE"),
+        ForeignKey("ab_role.id", ondelete="CASCADE"),
         nullable=False,
     ),
 )