Clean up unstable book

Author: JohnTitor

src/doc/unstable-book/src/language-features/const-in-array-repeat-expressions.md

@@ -2,7 +2,7 @@
 
 The tracking issue for this feature is: [#49147]
 
-[#44109]: https://github.com/rust-lang/rust/issues/49147
+[#49147]: https://github.com/rust-lang/rust/issues/49147
 
 ------------------------
 

src/doc/unstable-book/src/language-features/impl-trait-in-bindings.md

@@ -1,8 +1,8 @@
 # `impl_trait_in_bindings`
 
-The tracking issue for this feature is: [#34511]
+The tracking issue for this feature is: [#63065]
 
-[#34511]: https://github.com/rust-lang/rust/issues/34511
+[#63065]: https://github.com/rust-lang/rust/issues/63065
 
 ------------------------
 

src/doc/unstable-book/src/language-features/link-cfg.md

@@ -0,0 +1,5 @@
+# `link_cfg`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------

src/doc/unstable-book/src/language-features/trait-alias.md

@@ -2,7 +2,7 @@
 
 The tracking issue for this feature is: [#41517]
 
-[#41417]: https://github.com/rust-lang/rust/issues/41517
+[#41517]: https://github.com/rust-lang/rust/issues/41517
 
 ------------------------
 

src/doc/unstable-book/src/language-features/transparent-unions.md

@@ -2,7 +2,7 @@
 
 The tracking issue for this feature is [#60405]
 
-[60405]: https://github.com/rust-lang/rust/issues/60405
+[#60405]: https://github.com/rust-lang/rust/issues/60405
 
 ----
 

src/doc/unstable-book/src/library-features/read-initializer.md

@@ -0,0 +1,5 @@
+# `tidy_test_never_used_anywhere_else`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------