Screenshot: http://i.imgur.com/XbBuaIq.png
It is still there for me in the latest version.

In the profile folder which is usually:
C:\Users%USERNAME%\AppData\Roaming\Opera Software\Opera Stable
delete the file:
tracking_user_agent.json
This trick I found by its contents.

В папке профиля, которая обычно:
C:\Users%USERNAME%\AppData\Roaming\Opera Software\Opera Stable
удалите файл:
tracking_user_agent.json
Этот трюк я понял по его содержимому.