chore: Fix several style lints (#17488)

It's not comprehensive enough to start linting on `style` group, but
hey, it's a start.

Release Notes:

- N/A

crates/repl/src/repl_sessions_ui.rs

@@ -242,7 +242,7 @@ impl Render for ReplSessionsPage {
         for spec in kernel_specifications {
             kernels_by_language
                 .entry(spec.kernelspec.language.clone())
-                .or_insert_with(Vec::new)
+                .or_default()
                 .push(spec);
         }