CI: Use Node version defined in package.json

Makes it easier to bump versions.

.github/workflows/ci.yml

@@ -14,6 +14,6 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: '16'
+          node-version-file: 'package.json'
       - run: npm ci
       - run: npm run build