Auto merge of #49460 - kennytm:rollup, r=kennytm

Rollup of 12 pull requests

- Successful merges: #49243, #49329, #49364, #49400, #49405, #49427, #49428, #49429, #49439, #49442, #49444, #49452
- Failed merges:

1 files changed, 0 insertions, 23 deletions

diff --git a/src/doc/unstable-book/src/library-features/string-retain.md b/src/doc/unstable-book/src/library-features/string-retain.md
deleted file mode 100644
index 049444aa49b..00000000000
--- a/src/doc/unstable-book/src/library-features/string-retain.md
+++ /dev/null
@@ -1,23 +0,0 @@
-# `string_retain`
-
-The tracking issue for this feature is: [#43874]
-
-[#43874]: https://github.com/rust-lang/rust/issues/43874
-
-------------------------
-
-Retains only the characters specified by the predicate.
-
-In other words, remove all characters `c` such that `f(c)` returns `false`.
-This method operates in place and preserves the order of the retained
-characters.
-
-```rust
-#![feature(string_retain)]
-
-let mut s = String::from("f_o_ob_ar");
-
-s.retain(|c| c != '_');
-
-assert_eq!(s, "foobar");
-```