Replace async_trait with AFIT / RPITIT (#2308)

Co-authored-by: Jonas Platte <[email protected]>

examples/customize-path-rejection/src/main.rs

@@ -5,7 +5,6 @@
 //! ```
 
 use axum::{
-    async_trait,
     extract::{path::ErrorKind, rejection::PathRejection, FromRequestParts},
     http::{request::Parts, StatusCode},
     response::IntoResponse,
@@ -49,7 +48,6 @@ struct Params {
 // We define our own `Path` extractor that customizes the error from `axum::extract::Path`
 struct Path<T>(T);
 
-#[async_trait]
 impl<S, T> FromRequestParts<S> for Path<T>
 where
     // these trait bounds are copied from `impl FromRequest for axum::extract::path::Path`