tokio-xmpp: remove deny(unused) as long as it breaks nightly

Find a way to make it conditional on stable or something? Is that even
possible?

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

tokio-xmpp/src/lib.rs

@@ -1,6 +1,6 @@
 //! XMPP implementation with asynchronous I/O using Tokio.
 
-#![deny(unsafe_code, unused, missing_docs, bare_trait_objects)]
+#![deny(unsafe_code, missing_docs, bare_trait_objects)]
 
 mod starttls;
 mod stream_start;