Try to fix reports since dt 2.4 of jittery or too fast scrolling with
trackpad/touch on Quartz and X11. GDK_SMOOTH_SCROLL_MASK needs to be set
for Wayland to receive trackpad/touch events, but for X11 (and
Quartz?) these events are converted to regular scroll events if
GDK_SMOOTH_SCROLL_MASK is not set but GDK_SCROLL_MASK is.
I haven't seen bad scroll behavior for X11, but for safety's sake, am
eliminating this for X11 too.
(cherry picked from commit d30303b9)