Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       - name: Ensure line endings are consistent
         run: git config --global core.autocrlf input
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Load dependency cache
         uses: actions/cache@v4
         with:
@@ -56,7 +56,7 @@ jobs:
       - name: Ensure line endings are consistent
         run: git config --global core.autocrlf input
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Load dependency cache
         uses: actions/cache@v4
         with: