node: sync known sessions on disconnect

Make sure the service is current by removing disconnected peers.

Signed-off-by: Slack Coder <slackcoder@server.ky>

radicle-node/src/service.rs

@@ -566,8 +566,8 @@ where
 
                 self.reactor.connect(*addr);
             } else {
-                // TODO: Non-persistent peers should be removed from the
-                // map here or at some later point.
+                self.sessions.remove(&ip);
+                self.maintain_connections();
             }
         }
     }