Update Cargo submodule and its dependencies

Hopefully just another routine update!

So far this starts to enable the `std::arch` in stage0 builds of rustc.
This means that we may need stage0/not(stage0) in stdsimd itself, but
more and more code is starting to use `std::arch` so I think it's time
to start shifting the balance of work here.

src/libcore/lib.rs

@@ -251,9 +251,7 @@ macro_rules! vector_impl { ($([$f:ident, $($args:tt)*]),*) => { $($f!($($args)*)
 #[path = "../stdsimd/coresimd/mod.rs"]
 #[allow(missing_docs, missing_debug_implementations, dead_code, unused_imports)]
 #[unstable(feature = "stdsimd", issue = "48556")]
-#[cfg(not(stage0))] // allow changes to how stdsimd works in stage0
 mod coresimd;
 
 #[stable(feature = "simd_arch", since = "1.27.0")]
-#[cfg(not(stage0))]
 pub use coresimd::arch;