change vllm concurrency group

Author: jinyan-li1

.github/workflows/pr-vllm.yml

@@ -11,7 +11,7 @@ permissions:
   contents: read
 
 concurrency:
-  group: pr-${{ github.event.pull_request.number }}
+  group: pr-vllm-${{ github.event.pull_request.number }}
   cancel-in-progress: true
 
 jobs: