Fix fallout from coercion removal

src/libstd/io/stdio.rs

@@ -237,7 +237,7 @@ pub fn print(s: &str) {
 /// `\n` character is printed to the console after the string.
 pub fn println(s: &str) {
     with_task_stdout(|io| {
-        io.write(s.as_bytes()).and_then(|()| io.write([b'\n']))
+        io.write(s.as_bytes()).and_then(|()| io.write(&[b'\n']))
     })
 }