Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@2.24.0