Removed checks in gtksizerequest.c

Removed checks in gtksizerequest.c

Checks were in place to ensure that widgets never request taller
or wider than screen size. This was there to test a theory about
scrolled window children functioning correctly with dynamic content
however it breaks GtkViewport children which can generally return a
value taller than screen height intentionally, GtkViewport uses this
value to update the adjustments.