Change one-step dummy pipeline for testing (#1690)

Change the one-step dummy pipeline for testing

examples/community/one_step_unet.py

@@ -19,4 +19,6 @@ class UnetSchedulerOneForwardPipeline(DiffusionPipeline):
         model_output = self.unet(image, timestep).sample
         scheduler_output = self.scheduler.step(model_output, timestep, image).prev_sample
         
-        return scheduler_output
+        result = scheduler_output - scheduler_output + torch.ones_like(scheduler_output)
+
+        return result