fix clippy warnings in examples

examples/single_line.rs

@@ -38,8 +38,7 @@ fn main() -> io::Result<()> {
     let mut textarea = TextArea::default();
     textarea.set_cursor_line_style(Style::default());
     textarea.set_placeholder_text("Enter a valid float (e.g. 1.56)");
-    let layout =
-        Layout::default().constraints([Constraint::Length(3), Constraint::Min(1)].as_slice());
+    let layout = Layout::default().constraints([Constraint::Length(3), Constraint::Min(1)]);
     let mut is_valid = validate(&mut textarea);
 
     loop {