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

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         node-version: [20.x]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v6