[CI/Build][Doc] upgrade torch-npu to 0320 (#392)

### What this PR does / why we need it?
This pr upgrades torch-npu to 0320, so that #321,
https://github.com/vllm-project/vllm-ascend/issues/267#issuecomment-2745045743
could be fixed, and #372 should be reverted after this pr

### Does this PR introduce _any_ user-facing change?
upgrade torch-npu to 0320

### How was this patch tested?
tested locally with long seq inferencing.

---------

Signed-off-by: MengqingCao <cmq0113@163.com>

README.zh.md

@@ -39,7 +39,7 @@ vLLM 昇腾插件 (`vllm-ascend`) 是一个由社区维护的让vLLM在Ascend NP
 - 软件：
   * Python >= 3.9
   * CANN >= 8.0.RC2
-  * PyTorch >= 2.5.1, torch-npu >= 2.5.1.dev20250308
+  * PyTorch >= 2.5.1, torch-npu >= 2.5.1.dev20250320
   * vLLM (与vllm-ascend版本一致)
 
 ## 开始使用