Update benchmark directory for vLLM

[namanlalitnyu]

Changes

After vllm-project/vllm#25786, the base directories for benchmarking are updated, so inorder to make sure the vLLM continuous benchmarking works as expected, we need to update the directories here as well.

Testing

Once the vLLM Changes are merged, we need to verify that vLLM Benchmark workflow is working as expected.

[huydhn]

Ty for the fix!