Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/phpcs.yml

@@ -14,7 +14,7 @@ jobs:
     name: phpcs check codestyles
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP Action
         uses: shivammathur/setup-php@v2

.github/workflows/phpunit.yml

@@ -14,7 +14,7 @@ jobs:
     name: phpunit test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP Action
         uses: shivammathur/setup-php@v2

.github/workflows/static-analysis.yml

@@ -14,7 +14,7 @@ jobs:
     name: psalm static code analysis
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP Action
         uses: shivammathur/setup-php@v2