fix(test): fix _handle_low_balance mock signature to accept positional args

The gated_processor fixture's fake_low_balance mock used **kwargs, but
production code calls _handle_low_balance with positional args via
asyncio.to_thread. This caused a silent TypeError caught by the broad
except handler, making the handle_low_balance assertion fail (0 calls
instead of 1). Updated mock to match the actual method signature.

autogpt_platform/backend/backend/blocks/test/test_orchestrator_per_iteration_cost.py

@@ -492,8 +492,16 @@ def gated_processor(monkeypatch):
         fake_charge_extra,
     )
 
-    def fake_low_balance(self, **kwargs):
-        calls["handle_low_balance"].append(kwargs)
+    def fake_low_balance(
+        self, db_client, user_id, current_balance, transaction_cost
+    ):
+        calls["handle_low_balance"].append(
+            {
+                "user_id": user_id,
+                "current_balance": current_balance,
+                "transaction_cost": transaction_cost,
+            }
+        )
 
     monkeypatch.setattr(
         manager.ExecutionProcessor,