chore(deps): update actions/checkout action to v6 (#82)

Co-authored-by: mailersend-renovate[bot] <197618458+mailersend-renovate[bot]@users.noreply.github.com>
Co-authored-by: Peter Ocansey <ocanseypeter@gmail.com>

Author: mailersend-renovate[bot]

.github/workflows/php.yml

@@ -17,7 +17,7 @@ jobs:
     name: PHP ${{ matrix.php-versions }} Test on ${{ matrix.operating-system }}
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Setup PHP
       uses: shivammathur/setup-php@v2