Rollup merge of #140966 - est31:let_chains_library, r=tgross35

Remove #![feature(let_chains)] from library and src/librustdoc

PR #132833 has stabilized the `let_chains` feature. This PR removes the last occurences from the library, the compiler, and librustdoc (also because #140887 missed the conditional in one of the crates as it was behind the "rustc" feature).

We keep `core` as exercise for the future as updating it is non-trivial (see PR thread).

Author: fmease

compiler/rustc_pattern_analysis/src/lib.rs

@@ -6,7 +6,6 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
 #![allow(unused_crate_dependencies)]
-#![cfg_attr(all(feature = "rustc", bootstrap), feature(let_chains))]
 // tidy-alphabetical-end
 
 pub mod constructor;

library/std/src/lib.rs

@@ -305,7 +305,6 @@
 #![feature(iter_advance_by)]
 #![feature(iter_next_chunk)]
 #![feature(lang_items)]
-#![feature(let_chains)]
 #![feature(link_cfg)]
 #![feature(linkage)]
 #![feature(macro_metavar_expr_concat)]

src/librustdoc/lib.rs

@@ -11,7 +11,6 @@
 #![feature(if_let_guard)]
 #![feature(impl_trait_in_assoc_type)]
 #![feature(iter_intersperse)]
-#![feature(let_chains)]
 #![feature(never_type)]
 #![feature(round_char_boundary)]
 #![feature(test)]

tests/run-make/core-no-oom-handling/rmake.rs

@@ -6,7 +6,7 @@ use run_make_support::{rustc, source_root};
 
 fn main() {
     rustc()
-        .edition("2021")
+        .edition("2024")
         .arg("-Dwarnings")
         .crate_type("rlib")
         .input(source_root().join("library/core/src/lib.rs"))