Remove deprecated unstable ptr::Shared type alias.

It has been deprecated for about one release cycle.

Author: SimonSapin

src/libcore/cell.rs

@@ -146,13 +146,12 @@
 //!
 //! ```
 //! #![feature(core_intrinsics)]
-//! #![feature(shared)]
 //! use std::cell::Cell;
-//! use std::ptr::Shared;
+//! use std::ptr::NonNull;
 //! use std::intrinsics::abort;
 //!
 //! struct Rc<T: ?Sized> {
-//!     ptr: Shared<RcBox<T>>
+//!     ptr: NonNull<RcBox<T>>
 //! }
 //!
 //! struct RcBox<T: ?Sized> {

src/libcore/ptr.rs

@@ -2420,11 +2420,6 @@ impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
     }
 }
 
-/// Previous name of `NonNull`.
-#[rustc_deprecated(since = "1.25.0", reason = "renamed to `NonNull`")]
-#[unstable(feature = "shared", issue = "27730")]
-pub type Shared<T> = NonNull<T>;
-
 /// `*mut T` but non-zero and covariant.
 ///
 /// This is often the correct thing to use when building data structures using