xmpp: Replace unimplemented! and panic! with info! calls

It's great for debugging for fast-paced implementations but the codebase
has been more or less the same for years now (in a state we don't
exactly like, but it is what it is) and this is hindering things more
than helping.

Keep it at the INFO level nonetheless to make it more or less obvious
these things are not implemented.

Signed-off-by: pep <pep@bouah.net>

xmpp/src/disco/mod.rs

@@ -48,6 +48,6 @@ pub async fn handle_disco_info_result(agent: &mut Agent, disco: DiscoInfoResult,
             let _ = agent.client.send_stanza(iq).await;
         }
     } else {
-        unimplemented!("Ignored disco#info response from {}", from);
+        info!("Ignored disco#info response from {}", from);
     }
 }