remove let_chain feature

Summary:
X-link: meta-pytorch/monarch#1388

let_chains were stabilized in 1.88.0 for edition 2024 and removed in 1.90.0
rust-lang/rust#132833
rust-lang/rust#143214

Reviewed By: dtolnay

Differential Revision: D83221093

fbshipit-source-id: 6fb40aa7e1c282f453394db5b7f0dab1282c2e35

Author: cjlongoria

eden/mononoke/bookmarks/warm_bookmarks_cache/lib.rs

@@ -5,8 +5,6 @@
  * GNU General Public License version 2.
  */
 
-#![feature(let_chains)]
-
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::collections::HashSet;

eden/mononoke/cmdlib/mononoke_app/src/lib.rs

@@ -5,7 +5,6 @@
  * GNU General Public License version 2.
  */
 
-#![feature(let_chains)]
 #![feature(trait_alias)]
 
 mod app;

eden/mononoke/edenapi_service/src/lib.rs

@@ -6,7 +6,6 @@
  */
 
 #![feature(associated_type_defaults)]
-#![feature(let_chains)]
 #![feature(try_blocks)]
 
 pub mod context;

eden/mononoke/git_server/src/main.rs

@@ -7,7 +7,6 @@
 
 #![recursion_limit = "256"]
 #![feature(never_type)]
-#![feature(let_chains)]
 #![feature(cursor_split)]
 #![feature(try_blocks)]
 

eden/mononoke/hooks/src/lib.rs

@@ -7,7 +7,6 @@
 
 #![cfg_attr(not(fbcode_build), allow(unused_crate_dependencies))]
 #![cfg_attr(test, feature(trait_alias))]
-#![feature(let_chains)]
 
 pub mod errors;
 #[cfg(fbcode_build)]

eden/mononoke/lfs_server/src/main.rs

@@ -7,7 +7,6 @@
 
 #![recursion_limit = "256"]
 #![feature(never_type)]
-#![feature(let_chains)]
 
 use std::fs::File;
 use std::io::Write;