Remove unused import os in datasets (#4879)

* remove unused imports

* update lsun

Author: kazhang

torchvision/datasets/cifar.py

@@ -1,4 +1,3 @@
-import os
 import os.path
 import pickle
 from typing import Any, Callable, Optional, Tuple

torchvision/datasets/coco.py

@@ -1,4 +1,3 @@
-import os
 import os.path
 from typing import Any, Callable, Optional, Tuple, List
 

torchvision/datasets/lsun.py

@@ -1,5 +1,4 @@
 import io
-import os
 import os.path
 import pickle
 import string

torchvision/datasets/semeion.py

@@ -1,4 +1,3 @@
-import os
 import os.path
 from typing import Any, Callable, Optional, Tuple
 

torchvision/datasets/stl10.py

@@ -1,4 +1,3 @@
-import os
 import os.path
 from typing import Any, Callable, Optional, Tuple
 

torchvision/datasets/svhn.py

@@ -1,4 +1,3 @@
-import os
 import os.path
 from typing import Any, Callable, Optional, Tuple