test: set pressure to zero on proxout for the tablets with forced prox out

If a test goes past the tip-down threshold, the proximity timeout does not trigger. And one can spend a long time trying to debug why the test fails...

As far as I vaguely remember, these devices' pressure values are correct enough, it's just the lack of BTN_TOOL_PEN that is the issue so instead of a proper proximity out, we just send enough data to set the pressure to below the tip threshold.