fix actionlint

Signed-off-by: Junpu Fan <junpu@amazon.com>

Author: junpuf

.github/workflows/pr-example.yml

@@ -47,7 +47,7 @@ jobs:
           aws ecr get-login-password --region ${{ secrets.AWS_REGION }} | docker login --username AWS --password-stdin ${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.${{ secrets.AWS_REGION }}.amazonaws.com
           IMAGE_TAG=${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.${{ secrets.AWS_REGION }}.amazonaws.com/ci:vllm-0.10.2-gpu-py312-cu128-ubuntu22.04-rayserve-ec2-pr-${{ github.event.pull_request.number }}
           DOCKER_BUILDKIT=1 docker build --progress plain \
-            --build-arg CACHE_REFRESH=$(date +"%Y-%m-%d_%H") \
+            --build-arg CACHE_REFRESH="$(date +"%Y-%m-%d_%H")" \
             --tag "$IMAGE_TAG" \
             --target vllm-rayserve-ec2 \
             -f docker/vllm/Dockerfile.rayserve .