Remove OccupiedEntry::remove_pair

[unstable, deprecated since 1.12.0]

src/doc/unstable-book/src/SUMMARY.md

@@ -163,7 +163,6 @@
     - [linked_list_extras](library-features/linked-list-extras.md)
     - [lookup_host](library-features/lookup-host.md)
     - [manually_drop](library-features/manually-drop.md)
-    - [map_entry_recover_keys](library-features/map-entry-recover-keys.md)
     - [mpsc_select](library-features/mpsc-select.md)
     - [n16](library-features/n16.md)
     - [never_type_impls](library-features/never-type-impls.md)

src/doc/unstable-book/src/library-features/map-entry-recover-keys.md

@@ -1,5 +0,0 @@
-# `map_entry_recover_keys`
-
-The tracking issue for this feature is: [#34285]
-
-[#34285]: https://github.com/rust-lang/rust/issues/34285