Remove experimental jj UI, for now (#38743)

This PR removes the experimental jj bookmark picker that was added in
#30883.

This was just an exploratory prototype and while I would like to have
native jj UI at some point, I don't know when we'll get back to it.

Release Notes:

- N/A
28ed08340cMarshall Bowers committed on 9/23/2025, 9:40:22 PM· committed by GitHubparent74fe3b1
17 files changedLine totals unavailable