Fix the error of 'sample' key not found

The pipeline output looks like this currently
`ImagePipelineOutput(images=[<PIL.Image.Image image mode=RGB size=256x256 at 0x7F7190061A30>])`

app.py

@@ -14,7 +14,7 @@ def predict(prompt, steps=100, seed=42, guidance_scale=6.0):
     #torch.cuda.empty_cache()
     print(subprocess.check_output(["nvidia-smi"], stderr=subprocess.STDOUT).decode("utf8"))
     generator = torch.manual_seed(seed)
-    images = ldm_pipeline([prompt], generator=generator, num_inference_steps=steps, eta=0.3, guidance_scale=guidance_scale)["sample"]
+    images = ldm_pipeline([prompt], generator=generator, num_inference_steps=steps, eta=0.3, guidance_scale=guidance_scale)["images"]
     print(subprocess.check_output(["nvidia-smi"], stderr=subprocess.STDOUT).decode("utf8"))
     return images[0]