clean code

src/llamafactory/train/sft/metric.py

@@ -2,9 +2,10 @@ from dataclasses import dataclass
 from typing import TYPE_CHECKING, Dict, Sequence, Tuple, Union
 
 import numpy as np
+from transformers.utils import is_jieba_available, is_nltk_available
 
 from ...extras.constants import IGNORE_INDEX
-from ...extras.packages import is_jieba_available, is_nltk_available, is_rouge_available
+from ...extras.packages import is_rouge_available
 
 
 if TYPE_CHECKING: