The Air France flight status checker shows that, currently, flights from LHR arrive at Terminal 2E, and flights to Ljubljana leave from Terminal 2F.
https://wwws.airfrance.fr/en/flight-status
Note that this may change, so keep a close eye on your ticket and on the departure monitor, particularly upon arrival in CDG. You can (and should) ask the staff on board your inbound flight from London; tell them you have a tight connection. They may even announce the information (terminal and gate number) on board shortly before landing in Paris.