Experimental Tokenizer Fix

GPTNeoXTokenizer does not exist as a function so we use a GPT2 fallback, with this commit I hope that HF begins to use GPTNeoXTokenizerFast instead which does exist.

tokenizer_config.json

@@ -1 +1 @@
-{"unk_token": "<|endoftext|>", "bos_token": "<|endoftext|>", "eos_token": "<|endoftext|>", "add_prefix_space": false, "tokenizer_class": "GPTNeoXTokenizer"}
+{"unk_token": "<|endoftext|>", "bos_token": "<|endoftext|>", "eos_token": "<|endoftext|>", "add_prefix_space": false, "tokenizer_class": "GPTNeoXTokenizerFast"}