[misc] fit torch api upgradation and remove legecy import (#6093)

* [amp] fit torch's new api

* [amp] fix api call

* [amp] fix api call

* [misc] fit torch pytree api upgrade

* [misc] remove legacy import

* [misc] fit torch amp api

* [misc] fit torch amp api

docs/source/en/features/mixed_precision_training_with_booster.md

@@ -16,7 +16,7 @@ Author: [Mingyan Jiang](https://github.com/jiangmingyan)
 AMP stands for automatic mixed precision training.
 In Colossal-AI, we have incorporated different implementations of mixed precision training:
 
-1. torch.cuda.amp
+1. torch.amp
 2. apex.amp
 3. naive amp
 

docs/source/zh-Hans/features/mixed_precision_training_with_booster.md

@@ -16,7 +16,7 @@
 AMP 代表自动混合精度训练。
 在 Colossal-AI 中, 我们结合了混合精度训练的不同实现:
 
-1. torch.cuda.amp
+1. torch.amp
 2. apex.amp
 3. naive amp