Update actions/checkout action to v6 (#583)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         node-version: [18.x, 20.x, 22.x, 24.x]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v6
       with: