Apply clippy suggestion

Author: djc

imap-proto/examples/parse_response.rs

@@ -12,7 +12,7 @@ fn main() -> std::io::Result<()> {
             line
         };
 
-        match Response::from_bytes(line.replace("\n", "\r\n").as_bytes()) {
+        match Response::from_bytes(line.replace('\n', "\r\n").as_bytes()) {
             Ok((remaining, command)) => {
                 println!("{:#?}", command);