Fix failing test on Windows Platform (#11589)

* add separator for windows

* fixes test_is_copy_consistent on Windows

* fixing writing encoding issue on extended test (for Windows)

* resolving comments

tests/test_tokenization_wav2vec2.py

@@ -231,7 +231,7 @@ class Wav2Vec2TokenizerTest(unittest.TestCase):
         tokenizer_files = tokenizer.save_pretrained(tmpdirname2)
         self.assertSequenceEqual(
             sorted(tuple(VOCAB_FILES_NAMES.values()) + ("special_tokens_map.json", "added_tokens.json")),
-            sorted(tuple(x.split("/")[-1] for x in tokenizer_files)),
+            sorted(tuple(x.split(os.path.sep)[-1] for x in tokenizer_files)),
         )
 
         # Checks everything loads correctly in the same way