Update README.md (#2653)

* Update README.md

fix 2 bugs: (1) "previous_noisy_sample" should be in the FOR loop in line 87; (2) converting image to INT should be before "Image.fromarray" in line 91

* Apply suggestions from code review

---------
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

README.md

@@ -84,13 +84,12 @@ input = noise
 for t in scheduler.timesteps:
     with torch.no_grad():
         noisy_residual = model(input, t).sample
-
-previous_noisy_sample = scheduler.step(noisy_residual, t, input).prev_sample
-input = previous_noisy_sample
+        prev_noisy_sample = scheduler.step(noisy_residual, t, input).prev_sample
+        input = prev_noisy_sample
 
 image = (input / 2 + 0.5).clamp(0, 1)
 image = image.cpu().permute(0, 2, 3, 1).numpy()[0]
-image = Image.fromarray((image * 255)).round().astype("uint8")
+image = Image.fromarray((image * 255).round().astype("uint8"))
 image
 ```