Bump actions/checkout from 4 to 6 (#120)

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

Author: dependabot[bot]

.github/workflows/build.yml

@@ -55,7 +55,7 @@ jobs:
             update-constraints: "'--with=phpunit/phpunit:^11.2'"
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up PHP ${{ matrix.php-version }}
         uses: shivammathur/setup-php@v2