rls no longer builds after rust-lang/rust#79336

[rust-highfive]

Hello, this is your friendly neighborhood mergebot.
After merging PR #79336, I observed that the tool rls no longer builds.
A follow-up PR to the repository https://github.com/rust-lang/rls is needed to fix the fallout.

cc @camelid, do you think you would have time to do the follow-up work?
If so, that would be great!

[camelid]

Huh, how did this PR break rls? ripgrep doesn't show any use of optin_builtin_traits, and it compiled fine locally.

Do I need to wait until there's a nightly with the changes or something?

[Mark-Simulacrum]

RLS uses the rustc-ap-rustc_data_structures-686.0.0 crate which contains the optin_builtin_traits.

[camelid]

I think this might be a little too beyond my understanding of how to fix for now, so I'm unassigning myself.