st/nine: do not double-close the fd on teardown

As the newly introduced comment says:
 The pipe loader takes ownership of the fd

Thus, there's no need to close it again.

Cc: Patrick Rudolph <siro@das-labor.org>
Cc: Axel Davy <davyaxel0@gmail.com>
Cc: mesa-stable@lists.freedesktop.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Axel Davy <davyaxel0@gmail.com>
(cherry picked from commit 7b8d1b31)