Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: 📦 Check out the codebase
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: 🛠️ Setup PHP
         uses: shivammathur/setup-php@v2