Use production build of React for live Storybook deployment

[thyhjwb6]

Created from #2495

Our live version is not using the production build of React.

[github-actions[bot]]

This issue has been marked as stale because it has been open for 60 days with no activity

[jpveooys]

Looks like the production version is being used to me as profiling is unavailable:

Local:

https://storybook.design-system.digital.mod.uk:

A grep of the bundle also confirms react.production.min.js is included (and not react.development.js).

(The dev tools still otherwise mostly work in a prod build.)