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/editor/src/display_map/tab_map.rs

@@ -738,7 +738,7 @@ mod tests {
     fn test_random_tabs(cx: &mut gpui::App, mut rng: StdRng) {
         let tab_size = NonZeroU32::new(rng.gen_range(1..=4)).unwrap();
         let len = rng.gen_range(0..30);
-        let buffer = if rng.gen() {
+        let buffer = if rng.r#gen() {
             let text = util::RandomCharIter::new(&mut rng)
                 .take(len)
                 .collect::<String>();