Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/reusable-code-quality.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check existence of composer.json file
         id: check_composer_file
@@ -58,7 +58,7 @@ jobs:
 
     steps:
       - name: Check out source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check existence of composer.json & phpcs.xml.dist files
         id: check_files

.github/workflows/reusable-regenerate-readme.yml

@@ -18,7 +18,7 @@ jobs:
     if: ${{ github.repository_owner == 'wp-cli' && ! contains(fromJson('[".github", "wp-cli", "wp-cli-bundle", "wp-super-cache-cli", "php-cli-tools", "wp-config-transformer", "wp-cli.github.com"]'), github.event.repository.name) }}
     steps:
       - name: Check out source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up PHP environment
         uses: shivammathur/setup-php@v2

.github/workflows/reusable-testing.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Check out source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check existence of composer.json file
         id: check_files
@@ -127,7 +127,7 @@ jobs:
 
     steps:
       - name: Check out source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check existence of composer.json & behat.yml files
         id: check_files