chore(deps): update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/main.yml

@@ -13,7 +13,7 @@ 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
@@ -28,7 +28,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Use Node.js from .node-version
-      uses: actions/setup-node@v5
+      uses: actions/setup-node@v6
       with:
         node-version-file: .node-version
     - run: npm ci