Use lru_cache for tokenization tests (#36818)

* fix

* fix

* fix

* fix

---------

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

tests/models/deberta_v2/test_tokenization_deberta_v2.py

@@ -33,12 +33,13 @@ class DebertaV2TokenizationTest(TokenizerTesterMixin, unittest.TestCase):
     test_sentencepiece = True
     test_sentencepiece_ignore_case = True
 
-    def setUp(self):
-        super().setUp()
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
 
         # We have a SentencePiece fixture for testing
         tokenizer = DebertaV2Tokenizer(SAMPLE_VOCAB, unk_token="<unk>")
-        tokenizer.save_pretrained(self.tmpdirname)
+        tokenizer.save_pretrained(cls.tmpdirname)
 
     def get_input_output_texts(self, tokenizer):
         input_text = "this is a test"