Update namespaces inside torch.utils.data to the latest. (#13167)

* Update torch.utils.data namespaces to the latest.

* Format

* Update Dataloader.

* Style

examples/legacy/multiple_choice/utils_multiple_choice.py

@@ -77,7 +77,7 @@ class Split(Enum):
 
 if is_torch_available():
     import torch
-    from torch.utils.data.dataset import Dataset
+    from torch.utils.data import Dataset
 
     class MultipleChoiceDataset(Dataset):
         """