Set which servers to try and join upgraded rooms through

Fixes https://github.com/vector-im/riot-web/issues/7991

src/components/views/rooms/MessageComposer.js

@@ -285,6 +285,10 @@ export default class MessageComposer extends React.Component {
             action: 'view_room',
             highlighted: true,
             room_id: replacementRoomId,
+
+            // Try to join via the server that sent the event. This converts $something:example.org
+            // into a server domain by splitting on colons and ignoring the first entry ("$something").
+            via_servers: [this.state.tombstone.getId().split(':').splice(1).join(':')],
         });
     }