chore(deps): update actions/checkout action to v4

Author: renovate[bot]

Diff for: .github/workflows/php-ci.yaml

@@ -27,7 +27,7 @@ jobs:
     # https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs#excluding-matrix-configurations
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Setup PHP
       uses: shivammathur/setup-php@v2