[BUG] 关于qwen2的bug报告

datasets/utils.py文件中，关于qwen2的bug，**QWen2Tokenizer** 应该改为 **Qwen2Tokenizer**

`def get_bos_eos_token_ids(tokenizer):
if tokenizer.__class__.__name__ in [
'QWenTokenizer', 'QWen2Tokenizer', 'Qwen2TokenizerFast'
]:
bos_token_id = []
eos_token_id = tokenizer.eos_token_id
assert eos_token_id is not None, \
'Please set eos_token for Qwen tokenizer!'
elif tokenizer.__class__.__name__ == 'ChatGLMTokenizer':
bos_token_id = [64790, 64792]
eos_token_id = tokenizer.eos_token_id
else:
bos_token_id = tokenizer.bos_token_id
eos_token_id = tokenizer.eos_token_id
if isinstance(bos_token_id, int):
bos_token_id = [bos_token_id]
if isinstance(eos_token_id, int):
eos_token_id = [eos_token_id]
return bos_token_id, eos_token_id
`

Open datasets/utils.py and inspect get_bos_eos_token_ids, especially the tokenizer class-name list. Correct the QWen2Tokenizer spelling to Qwen2Tokenizer and verify that the Qwen2 branch recognizes the intended class name.

Written by the indexing model from the issue text.