selftests/hid: tablets: do not set invert when the eraser is used

Turns out that the chart from Microsoft is not exactly what I got here:
when the rubber is used, and is touching the surface, invert can (should)
be set to 0...

[0] https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/windows-pen-states



Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Jiri Kosina <jkosina@suse.com>
Link: https://lore.kernel.org/r/20231206-wip-selftests-v2-7-c0350c2f5986@kernel.org


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