Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
 
         steps:
             - name: "Checkout"
-              uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+              uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
             - name: "Install PHP"
               uses: "shivammathur/setup-php@9e72090525849c5e82e596468b86eb55e9cc5401" # v2