Their official contract of carriage states:
8.1.9. If a passenger does not show up for the flight («No-Show») where he/she has confirmed reservations and fails to inform the air
carrier about changes in his/her travel in advance, the air carrier
shall be entitled to cancel the reservation for this flight and for
the next segments of the route and the return flight.
As you see, there are no fees mentioned here (unlike many other places, like 6.3).
However if you're really worried about it, according to the contract all you need to do to avoid a "no-show" situation is to notify the airline in advance about changes in your travel plans. There is no documented procedure for that, but in my personal opinion calling/emailing the airline and telling them you're not coming on that flight due to change in you plans should constitute such notification. Or tell the service/gate agent when you're at the airport.
I couldn't find any source of why they mentioned this fee for a no-show, but most likely KateGregory's comment is right - this "fee" is used to drain the value of the ticket - including airport taxes and fees - to zero in case of no-show, making it impossible for you to claim a refund.