refactor(example): remove redundant vec![] in user_input example (#26)

Co-authored-by: rhysd <lin90162@yahoo.co.jp>

examples/user_input.rs

@@ -183,7 +183,7 @@ fn ui<B: Backend>(f: &mut Frame<B>, app: &App) {
         .iter()
         .enumerate()
         .map(|(i, m)| {
-            let content = vec![Spans::from(Span::raw(format!("{}: {}", i, m)))];
+            let content = Spans::from(Span::raw(format!("{}: {}", i, m)));
             ListItem::new(content)
         })
         .collect();