Update actions/checkout action to v6

.gitea/workflows/build-base.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3