This changes to publish TED's canonical app port, `4200`.
What's wrong with the currently used ports?
57f63003ef/app/app.ts (L18-L20)
Quoting here:
> 8000, // Past static webserver port, to be removed, after switching to
4200, clashes with CloudServices on CI.
> 5000, // Past Postgraphile port, to be removed, after switching to
4200, clashes with macOS AirDrop.
> 3000, // Past Gitea port, to be removed, after removing Gitea, because
it clashes with `yarn start` in Appsmith.
/ok-to-test tags="@tag.Sanity"
85bed5bfc7