os_str_str_ref_eq feature marked stable since 1.28.0 instead of 1.29.0

[mmerickel]

I noticed that https://blog.rust-lang.org/2018/09/13/Rust-1.29.html mentioned #51178 and it is marked #[stable(feature = "os_str_str_ref_eq", since = "1.28.0")]. Shouldn't that be 1.29.0?

https://github.com/rust-lang/rust/blob/1.29.0/src/libstd/ffi/os_str.rs#L420-L432