rls no longer builds after rust-lang/rust#74653

[rust-highfive]

Hello, this is your friendly neighborhood mergebot.
After merging PR #74653, 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 @petrochenkov, do you think you would have time to do the follow-up work?
If so, that would be great!

And nominating for compiler team prioritization.