Auto merge of #146636 - Mark-Simulacrum:bootstrap-bump, r=jieyouxu

Bump bootstrap compiler to 1.91 beta

https://forge.rust-lang.org/release/process.html#default-branch-bootstrap-update-tuesday

Author: bors

clippy_lints/src/lib.rs

@@ -7,7 +7,6 @@
 #![feature(iter_intersperse)]
 #![feature(iter_partition_in_place)]
 #![feature(never_type)]
-#![cfg_attr(bootstrap, feature(round_char_boundary))]
 #![feature(rustc_private)]
 #![feature(stmt_expr_attributes)]
 #![feature(unwrap_infallible)]

tests/missing-test-files.rs

@@ -1,6 +1,5 @@
 #![warn(rust_2018_idioms, unused_lifetimes)]
 #![allow(clippy::assertions_on_constants)]
-#![cfg_attr(bootstrap, feature(path_file_prefix))]
 
 use std::cmp::Ordering;
 use std::ffi::OsStr;