Update config.json

updated the tokenizer_class to MT5Tokenizer

config.json

@@ -19,6 +19,6 @@
   "pad_token_id": 0,
   "relative_attention_num_buckets": 32,
   "tie_word_embeddings": false,
-  "tokenizer_class": "T5Tokenizer",
+  "tokenizer_class": "MT5Tokenizer",
   "vocab_size": 250112
 }