Your flight schedule being changed to 40 mins connection doesn't necessarily mean that the airport Minimum Connection Time has changed (QR website still says 45, or 60 for US). Keep an eye on the booking, you may find it is no longer showing as "confirmed", or your onward flight gets rebooked to a later departure.

Alternatively you may wish to call or use the live chat to confirm either that it is still OK at 40 mins, or have some alternatives in mind for a rebooking.