Update edition to 2021

- Remove TryFrom/Into and FromIterator imports
- Prevent impl_validator_using_provider macro in sasl crate from
  constructing trait object

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

tokio-xmpp/src/client/bind.rs

@@ -1,5 +1,4 @@
 use futures::stream::StreamExt;
-use std::convert::TryFrom;
 use std::marker::Unpin;
 use tokio::io::{AsyncRead, AsyncWrite};
 use xmpp_parsers::bind::{BindQuery, BindResponse};