Use newer checkouts version for GHA

Author: paragonie-security

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2