Pin rollup version to 3.19.1

[IanVS]

Closes #

Attempting to get next green again in CI, by pinning rollup to 3.19.1, the version prior to that which was released yesterday (3.20.0), which I suspect is causing our problems.

What I did

I also needed to hack in a TS ignore, and I regenerated the lockfile.

And I unpinned Vite, which had no effect: #21715

How to test

It's not possible to test locally, it seems. But hopefully CI will show us.

I wonder if we need to try to limit ourselves to a single CPU locally, somehow, to me more like CI… 🤔

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[IanVS]

OK, it does seem to be rollup that has caused this problem. The chromatic and e2e sandboxes are passing in this PR (though there are some other, seemingly unrelated issues which cause ci checks to be red above).

[IanVS]

I have reported this issue in rollup/rollup#4916.