Fix wrong output on 3n-1 steps count

Author: StAlKeR7779

src/diffusers/schedulers/scheduling_dpmsolver_singlestep.py

@@ -248,6 +248,10 @@ def get_order_list(self, num_inference_steps: int) -> List[int]:
                 orders = [1, 2] * (steps // 2)
             elif order == 1:
                 orders = [1] * steps
+
+        if self.config.final_sigmas_type == "zero":
+            orders[-1] = 1
+
         return orders
 
     @property