ci: upgrade actions/checkout to v5 for Node.js 24 support

.github/workflows/serverlist-validate.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Compare Versions
         run: chmod +x .github/workflows/serverlist-validate.sh; .github/workflows/serverlist-validate.sh