style: Remove duplicate function call (#989)

Co-authored-by: Lucio Franco <luciofranco14@gmail.com>

src/message.rs

@@ -53,7 +53,7 @@ pub trait Message: Debug + Send + Sync {
     {
         let required = self.encoded_len();
         let remaining = buf.remaining_mut();
-        if required > buf.remaining_mut() {
+        if required > remaining {
             return Err(EncodeError::new(required, remaining));
         }