Build node-version seems to be ignored

[ascheucher-shopify-partner]

I am following the Deploy your Astro Site to GitHub Pages manual, but always get following warning:

build
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: pnpm/action-setup@v2. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

The .github/workflows/deploy.yml file looks fine to me:

name: Deploy the AstroBlogTutorial to GitHub Pages

on:
  # Trigger the workflow every time you push to the `main` branch
  # Using a different branch name? Replace `main` with your branch’s name
  push:
    branches: [ main ]
  # Allows you to run this workflow manually from the Actions tab on GitHub.
  workflow_dispatch:

# Allow this job to clone the repo and create a page deployment
permissions:
  contents: read
  pages: write
  id-token: write

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout your repository using git
        uses: actions/checkout@v4
      - name: Install, build, and upload your site
        uses: withastro/action@v2
        with:
          node-version: 20

  deploy:
    needs: build
    runs-on: ubuntu-latest
    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}
    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4

Is this a bug, or my error? I am new to GitHub actions...