Update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: ${{ matrix.node-version }}
       - run: npm ci