chore: Bump Rust version to 1.86 (#28021)

Closes #ISSUE

Release Notes:

- N/A

crates/project_panel/src/project_panel.rs

@@ -3259,7 +3259,7 @@ impl ProjectPanel {
                                         .take(prefix_components)
                                         .collect::<PathBuf>();
                                     if let Some(last_component) =
-                                        Path::new(processing_filename).components().last()
+                                        Path::new(processing_filename).components().next_back()
                                     {
                                         new_path.push(last_component);
                                         previous_components.next();