drirc: add Spectacle, Falkon to a-sync blacklist

Spectacle is the plasma screenshot utility.

It will freeze the whole screen and then let the user select an area on the screen to capture. During this operation, frame rate jumps between 0 and max, which is worst case for adaptive sync, potentially introducing flicker and corruption. Please note that you won't be able to observe this behaviour if running a compositor.

Falkon is a KDE web browser that should succeed Konqueror. Web browsers are known-bad use cases for adaptive sync.