Update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
     name: ${{ matrix.os }} (host=${{ matrix.host }}, target=${{ matrix.target }})
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: ${{ matrix.node }}
           architecture: ${{ matrix.host }}