Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
         php-versions: ['7.4', '8.0', '8.1', '8.2']
         composer-flags: ['', '--prefer-lowest']
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -39,7 +39,7 @@ jobs:
     name: PHP coverage
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -60,7 +60,7 @@ jobs:
     name: Quality checks
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2