[Bugfix] Align vllm version in requirements-test.txt with pyproject.toml

[arijitroy003]

Summary

requirements-test.txt pinned vllm==0.9.2, but pyproject.toml specifies vllm==0.13.0 in the test and lmcache optional dependencies, causing test environment version inconsistency.

Changes

• Updated requirements-test.txt: vllm==0.9.2 → vllm==0.13.0

Testing

Verified by grep that vllm versions now match across both files.

[gemini-code-assist]

Code Review

This pull request updates the vllm dependency version from 0.9.2 to 0.13.0 in requirements-test.txt. There are no review comments, and I have no feedback to provide.