Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/codeception_ci.yml

@@ -10,7 +10,7 @@ jobs:
       runs-on: ubuntu-latest
       steps:
         - name: Checkout
-          uses: actions/checkout@v5
+          uses: actions/checkout@v6
         - name: Install PHP
           uses: shivammathur/setup-php@v2
           with: