docs.rs build is failing

[SOF3]

https://docs.rs/crate/core2/0.4.0/builds/501312

[INFO] [stderr]  Documenting core2 v0.4.0 (/opt/rustwide/workdir)
[INFO] [stderr] error[E0635]: unknown feature `read_initializer`
[INFO] [stderr]  --> src/lib.rs:3:64
[INFO] [stderr]   |
[INFO] [stderr] 3 | #![cfg_attr(all(feature = "std", feature = "nightly"), feature(read_initializer))]
[INFO] [stderr]   |                                                                ^^^^^^^^^^^^^^^^
[INFO] [stderr] 

seems that docs.rs runs cargo doc with --features nightly by default, but this feature no longer exists as per rust-lang/rust#42788.