[Unet1d] correct docs (#2565)

src/diffusers/models/unet_1d.py

@@ -195,7 +195,7 @@ class UNet1DModel(ModelMixin, ConfigMixin):
     ) -> Union[UNet1DOutput, Tuple]:
         r"""
         Args:
-            sample (`torch.FloatTensor`): `(batch_size, sample_size, num_channels)` noisy inputs tensor
+            sample (`torch.FloatTensor`): `(batch_size, num_channels, sample_size)` noisy inputs tensor
             timestep (`torch.FloatTensor` or `float` or `int): (batch) timesteps
             return_dict (`bool`, *optional*, defaults to `True`):
                 Whether or not to return a [`~models.unet_1d.UNet1DOutput`] instead of a plain tuple.