See rust-lang/rust#138907 for more details, specifically the latest commit therein.
The following two commits in the repo:
remove the remaining uses of doc_auto_cfg but are not part of any stable release.
For context, this prevents building the docs for the rust bindings of glib based libraries using gtk-rs, for example, the failing CI job https://gitlab.gnome.org/msandova/soup3-rs/-/jobs/6049005 for https://gitlab.gnome.org/World/Rust/soup3-rs/-/merge_requests/36.
Would it be possible to backport the required changes and do a small release?