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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         python-version: ['3.x']
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}

.github/workflows/integration.yml

@@ -25,7 +25,7 @@ jobs:
           sudo apt-get remove --purge nginx*
           sudo apt-get autoremove
           sudo apt-get autoclean
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions/setup-python@v6

.github/workflows/wp-cli-version-check.yml

@@ -13,7 +13,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Get latest WP-CLI version
         id: get-version