[ci] bump actions/checkout

Pick up security fixes: https://github.com/actions/checkout#checkout-v7

Author: nil4

.github/workflows/publish.yml

@@ -27,7 +27,7 @@ jobs:
 
     steps:
     - name: Checkout
-      uses: actions/checkout@v6
+      uses: actions/checkout@v7
       with:
         fetch-depth: 0
         persist-credentials: false