fix: failing english builds

[scissorsneedfoodtoo]

Checklist:

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)

This PR sets the timeout for Piscina explicitly to prevent parallel processing of posts / pages from timing out under the hood, and increases batch sizes for fetched posts / pages that are processed.

Edit: Tested and English builds do complete, but can be a bit flaky due to the way we fetch the trending.json files from the CDN.

By doing the following things we should fix the flakiness, and help bring more parts of the repo up-to-date:

• Download trending.json before the builds similar to the way we do in the main repo
• Require Node v20 in package.json and bump the versions in the GHA workflows (after testing with Ghost builds)
• Cleanup Crowdin GHA so we can use Ubuntu 24.04 everywhere (remove Firefox downgrade step)