chore: Bump Rust version to 1.88 (#33439)

Goodies in this version:
- if-let chains 🎉
- Better compiler perf for Zed
(https://github.com/rust-lang/rust/pull/138522)

For more, see: https://releases.rs/docs/1.88.0/

Release Notes:

- N/A

---------

Co-authored-by: Junkui Zhang <364772080@qq.com>

crates/buffer_diff/src/buffer_diff.rs

@@ -1867,7 +1867,7 @@ mod tests {
             let hunk = diff.hunks(&buffer, cx).next().unwrap();
 
             let new_index_text = diff
-                .stage_or_unstage_hunks(true, &[hunk.clone()], &buffer, true, cx)
+                .stage_or_unstage_hunks(true, std::slice::from_ref(&hunk), &buffer, true, cx)
                 .unwrap()
                 .to_string();
             assert_eq!(new_index_text, buffer_text);