backends/x11: Drop warning about libinput property item count

libinput 1.3 introduced a custom acceleration profile extending the related properties from 2 to 3 items, which now triggering this warning. This does not have a functional impact since GNOME currently does not make use of the new profile. Also increasing the libinput version dependency which would be needed to change the expected item count is not possible in a stable release either. So just drop this warning to be compatible with newer versions of libinput.

See: https://gitlab.freedesktop.org/xorg/driver/xf86-input-libinput/-/merge_requests/39#note_1656566 Closes: #2987 (closed)