hw/xwin: Drop call to setlocale()

Since we now only work with UTF-8 (or ISO8859-1) text in the clipboard,
we don't need to setlocale().
5 jobs for clipboard in 7 minutes and 49 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Docker Image
passed #2290523
debian-testing

00:01:17

 
  Build And Test
passed #2290524
autotools

00:06:31

passed #2290525
meson

00:02:44

passed #2290526
meson-noglamor

00:02:33

 
  External
passed continuous-integration/appveyor/branch