selftests/hid: wacom: fix confidence tests

The device is exported with a fuzz of 4, meaning that the `+ t` here
is removed by the fuzz algorithm, making those tests failing.

Not sure why, but when I run this locally it was passing, but not in the
VM of the CI.

Fixes: b0fb904d ("HID: wacom: Add additional tests of confidence behavior")
Link: https://gitlab.freedesktop.org/bentiss/hid/-/jobs/53692957#L3315


Acked-by: Jason Gerecke <jason.gerecke@wacom.com>
Link: https://lore.kernel.org/r/20240117-b4-wip-wacom-tests-fixes-v1-1-f317784f3c36@kernel.org


Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>