Bump actions/checkout from 2 to 4 (#10)

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] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/php.yml

@@ -28,7 +28,7 @@ jobs:
     name: Symfony ${{ matrix.symfony }}, ${{ matrix.dep }} deps, PHP ${{ matrix.php }}, ${{ matrix.operating-system }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Install PHP
       uses: shivammathur/setup-php@v2

.github/workflows/split.yml

@@ -31,7 +31,7 @@ jobs:
                         split_repository: 'gotenberg-pdf-bundle'
 
         steps:
-            -   uses: actions/checkout@v2
+            -   uses: actions/checkout@v4
 
             # no tag
             -