chore: remove repetitive words in comment (#3619)

Signed-off-by: crazehang <zhangrenzhong@outlook.com>

examples/send_file.rs

@@ -49,7 +49,7 @@ async fn response_examples(
     match (req.method(), req.uri().path()) {
         (&Method::GET, "/") | (&Method::GET, "/index.html") => simple_file_send(INDEX).await,
         (&Method::GET, "/no_file.html") => {
-            // Test what happens when file cannot be be found
+            // Test what happens when file cannot be found
             simple_file_send("this_file_should_not_exist.html").await
         }
         _ => Ok(not_found()),

src/client/dispatch.rs

@@ -40,7 +40,7 @@ pub(crate) struct Sender<T, U> {
     /// without notice.
     #[cfg(feature = "http1")]
     buffered_once: bool,
-    /// The Giver helps watch that the the Receiver side has been polled
+    /// The Giver helps watch that the Receiver side has been polled
     /// when the queue is empty. This helps us know when a request and
     /// response have been fully processed, and a connection is ready
     /// for more.