Bump actions/checkout from 2 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/php-cs-fixer.yml

@@ -8,7 +8,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           ref: ${{ github.head_ref }}
 

.github/workflows/phpstan.yml

@@ -11,7 +11,7 @@ jobs:
     name: phpstan
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2

.github/workflows/run-tests.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2

.github/workflows/update-changelog.yml

@@ -10,7 +10,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           ref: main