fix: Typo

[Cherrling]

在某些较低版本的 torch/python 版本中，可能会触发找不到 AdamW 优化器，改为正确大小写拼写可解决

# cherrling @ viper in ~/code/DWSF on git:main x [8:51:24]
$ ./train_ed.sh
Traceback (most recent call last):
  File "train_ed.py", line 64, in <module>
    optimizer = torch.optim.Adamw(encoder_decoder.parameters(), lr=1e-4)
AttributeError: module 'torch.optim' has no attribute 'Adamw'