fix(dns): remove Clone boundary on Transport

Follow on to libp2p#2529

Author: dignifiedquire

transports/dns/src/lib.rs

@@ -175,7 +175,7 @@ where
 
 impl<T, C, P> Transport for GenDnsConfig<T, C, P>
 where
-    T: Transport + Clone + Send + 'static,
+    T: Transport + Send + 'static,
     T::Error: Send,
     T::Dial: Send,
     C: DnsHandle<Error = ResolveError>,
@@ -235,7 +235,7 @@ where
 
 impl<T, C, P> GenDnsConfig<T, C, P>
 where
-    T: Transport + Clone + Send + 'static,
+    T: Transport + Send + 'static,
     T::Error: Send,
     T::Dial: Send,
     C: DnsHandle<Error = ResolveError>,