[BUILD] Upgrade torch-npu to 2.5.1 (#661)

### What this PR does / why we need it?
The torch-npu 2.5.1 are published:
https://pypi.org/project/torch-npu/2.5.1/
It's time to remove all torch-npu dev version from vllm-ascend code base

### Does this PR introduce _any_ user-facing change?
Yes, using torch-npu 2.5.1

### How was this patch tested?
- [ ] CI passed
- [ ] Manually test
- [ ] Grep all `dev2025`

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Signed-off-by: Yikun Jiang <yikunkero@gmail.com>

requirements.txt

@@ -9,6 +9,7 @@ pyyaml
 scipy
 setuptools>=64
 setuptools-scm>=8
+torch-npu==2.5.1
 torch>=2.5.1
 torchvision<0.21.0
 wheel