Allow clippy::rc_buffer only where it's not easily fixed

src/lib.rs

@@ -67,7 +67,6 @@
 
 #![deny(rust_2018_idioms)]
 #![allow(clippy::needless_doctest_main, clippy::type_complexity)]
-#![allow(clippy::rc_buffer)] // FXIME: We should take a closer look for the warnings at some point.
 #![doc(html_logo_url = "https://actix.rs/img/logo.png")]
 #![doc(html_favicon_url = "https://actix.rs/favicon.ico")]
 

src/route.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::rc_buffer)] // inner value is mutated before being shared (`Rc::get_mut`)
+
 use std::future::Future;
 use std::pin::Pin;
 use std::rc::Rc;