Rollup merge of rust-lang#145336 - clarfonthey:hidden-unicode, r=ibraheemdev

Hide docs for `core::unicode`

This module is perma-unstable and shouldn't show up in the public docs. If people want to see the docs for it, they can still run `RUSTDOCFLAGS=--document-hidden-items ./x doc library/core`.

Author: jieyouxu

library/core/src/unicode/mod.rs

@@ -1,5 +1,6 @@
+//! Unicode internals used in liballoc and libstd. Not public API.
 #![unstable(feature = "unicode_internals", issue = "none")]
-#![allow(missing_docs)]
+#![doc(hidden)]
 
 // for use in alloc, not re-exported in std.
 #[rustfmt::skip]
@@ -31,5 +32,4 @@ mod unicode_data;
 ///
 /// The version numbering scheme is explained in
 /// [Unicode 11.0 or later, Section 3.1 Versions of the Unicode Standard](https://www.unicode.org/versions/Unicode11.0.0/ch03.pdf#page=4).
-#[stable(feature = "unicode_version", since = "1.45.0")]
 pub const UNICODE_VERSION: (u8, u8, u8) = unicode_data::UNICODE_VERSION;