test: fix edge-scroll no-motion test

test: fix edge-scroll no-motion test

The test is supposed to make sure no motion event is sent and that scrolling
continues once leaving the edge. It does so by moving down the edge, into the
touchpad, then down further. The move from the edge into the touchpad had a
vertical component to it though and could cause the scroll minimum test to
fail. This is currently covered up by the delta calculations though, but fix
it anyway.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>