Investigate rails-ujs dependency

[Bubballoo3]

This came up in my investigation of #4885, where it seems like rails-ujs is an earlier alternative to turbo-rails. To avoid conflicts in the future, we should likely move anything depending on rails-ujs functionality to use turbo instead, so we can drop rails-ujs before the next rails upgrade

[johrstrom]

This may be required for #5058, so that's why we're scheduling it in 4.2. If it needs to be done to complete 5058, then we'll do it because we have to. Otherwise we can defer it to some other release.