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/terminal/src/terminal_settings.rs

@@ -5,7 +5,7 @@ use collections::HashMap;
 use gpui::{
     px, AbsoluteLength, App, FontFallbacks, FontFeatures, FontWeight, Pixels, SharedString,
 };
-use schemars::{gen::SchemaGenerator, schema::RootSchema, JsonSchema};
+use schemars::{r#gen::SchemaGenerator, schema::RootSchema, JsonSchema};
 use serde_derive::{Deserialize, Serialize};
 use settings::{add_references_to_properties, SettingsJsonSchemaParams, SettingsSources};
 use std::path::PathBuf;