ci: bump actions/checkout to v4

Author: checkout‑bot

.github/workflows/docker-coordinator-api-arm64.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Set up QEMU
         run: |
           docker run --rm --privileged multiarch/qemu-user-static --reset -p yes