xfree86/inputtest: Drop extraneous linux-specific include

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
4 jobs for xfree86-inputtest-drop-include in 3 minutes and 22 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Docker Image
passed debian-buster #6482696

00:00:17

 
  Build And Test
passed autotools #6482697

00:03:05

passed meson #6482698

00:01:02

passed meson-noglamor #6482699

00:00:57