Fix CORS credentials on app-dev reverse-proxy preflight - #8320

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: Shopify/shopify-cla-action@9938f4b43524d1cfa7471ce9a803edf226697284. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/