[UT] fix skip ut test for test_torchair_deepseek

[zhangxinyuehfad]

What this PR does / why we need it?

[UT] fix skip ut test for test_torchair_deepseek

Does this PR introduce any user-facing change?

How was this patch tested?

• vLLM version: v0.11.0rc3
• vLLM main: vllm-project/vllm@c9461e0

[github-actions]

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[gemini-code-assist]

Code Review

This pull request fixes skipped unit tests in test_torchair_deepseek_v2.py by introducing a mock_ascend_config fixture to mock the global _ASCEND_CONFIG. The approach is correct and allows the tests to run. My review includes one suggestion to improve the maintainability of the test code by centralizing the mock configuration and removing duplication.