Fixes <https://issues.guix.gnu.org/35450>.
This driver isn't intended to be installed by default as it takes
precedence over the recommended xf86-input-libinput.
* gnu/services/xorg.scm (%default-xorg-modules): Remove
xf86-input-synaptics.
Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>