Disable Unredirect Fullscreen Windows by default

Well we don't have another choice if half of the drivers crash kwin
whenever you watch a fullscreen flash video or use a screen saver.
Unredirect Fullscreen Window was quite useful in case you used
to play heavy OpenGL games, but pretty useless for anything else.
For the game and hd video usecase we nowadays have the better way
of really suspending compositing (either by the client indicating or
with a window specific rule). The plus of suspending compositing is
that the driver doesn't crash.

And yes we are "supposed" to no longer workaround driver bugs.
Good joke, I like to redirect my inbox to everyone who things we
are not allowed to workaround driver bugs.

CCBUG: 252817