Bump actions/checkout from 5 to 6 (#38)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  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/test.yml

@@ -24,7 +24,7 @@ jobs:
       versions: ${{ steps.php-matrix.outputs.versions }}
       highest: ${{ steps.php-matrix.outputs.highest }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           sparse-checkout: composer.json
           sparse-checkout-cone-mode: false
@@ -46,7 +46,7 @@ jobs:
             coverage: xdebug
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: shivammathur/setup-php@v2
         with:
@@ -81,7 +81,7 @@ jobs:
     permissions:
       id-token: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: actions/download-artifact@v6
         with: