fix: use native git instead of actions/checkout to avoid missing nodejs

.gitea/workflows/autograde.yml

@@ -34,9 +34,12 @@ jobs:
           rm -rf /var/lib/apt/lists/*
       
       - name: Checkout code
-        uses: actions/checkout@v3
-        with:
-          fetch-depth: 1
+        run: |
+          git config --global --add safe.directory ${{ github.workspace }}
+          git init
+          git remote add origin ${{ github.server_url }}/${{ github.repository }}.git
+          git fetch --depth=1 origin ${{ github.sha }}
+          git checkout ${{ github.sha }}
       
       - name: Fix permissions
         run: chown -R $(whoami):$(whoami) ${{ github.workspace }} || true