Update docstring (huggingface#1971)

Author: Warvito

src/diffusers/schedulers/scheduling_pndm.py

@@ -84,8 +84,7 @@ class PNDMScheduler(SchedulerMixin, ConfigMixin):
             otherwise it uses the value of alpha at step 0.
         prediction_type (`str`, default `epsilon`, optional):
             prediction type of the scheduler function, one of `epsilon` (predicting the noise of the diffusion
-            process), `sample` (directly predicting the noisy sample`) or `v_prediction` (see section 2.4
-            https://imagen.research.google/video/paper.pdf)
+            process) or `v_prediction` (see section 2.4 https://imagen.research.google/video/paper.pdf)
         steps_offset (`int`, default `0`):
             an offset added to the inference steps. You can use a combination of `offset=1` and
             `set_alpha_to_one=False`, to make the last step use step 0 for the previous alpha product, as done in