When favoriting/reprioritizng a room, make sure to re-sort the list

This fixes some odd issues like newly favorited rooms being sent to the
bottom of the room list, and so on.

(cherry picked from commit 78beb9ffff)

src/rooms/models/roomtreemodel.cpp

@@ -163,6 +163,9 @@ void RoomTreeModel::moveRoom(Quotient::Room *room)
     beginInsertRows(newParent, newParentItem->childCount(), newParentItem->childCount());
     newParentItem->insertChild(std::make_unique<RoomTreeItem>(neochatRoom, newParentItem));
     endInsertRows();
+
+    // The room list needs to be re-sorted when this happens, of course.
+    Q_EMIT invalidateSort();
 }
 
 void RoomTreeModel::connectRoomSignals(NeoChatRoom *room)