chore: Prepare for Rust edition bump to 2024 (without autofix) (#27791)

Successor to #27779 - in this PR I've applied changes manually, without
futzing with if let lifetimes at all.

Release Notes:

- N/A

crates/context_server_settings/src/context_server_settings.rs

@@ -2,7 +2,7 @@ use std::sync::Arc;
 
 use collections::HashMap;
 use gpui::App;
-use schemars::gen::SchemaGenerator;
+use schemars::r#gen::SchemaGenerator;
 use schemars::schema::{InstanceType, Schema, SchemaObject};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};