Change DL Url

As suggested in https://github.com/huggingface/datasets-server/issues/942#issuecomment-1471972194

fashion_mnist_corrupted.py

@@ -39,7 +39,7 @@ else:
     raise ValueError("Unsupported version.")
 
 _URL = (
-    f"https://github.com/testingautomated-usi/fashion-mnist-c/raw/{tag}/generated/npy/"
+    f"https://raw.githubusercontent.com/testingautomated-usi/fashion-mnist-c/{tag}/generated/npy/"
 )
 
 _URLS = {