Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/phpcs.yml

@@ -14,7 +14,7 @@ jobs:
         php-version: ['8.0', '8.1', '8.2']
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install PHP
         uses: shivammathur/setup-php@v2