useradd-example: package typo correction

Fixes [YOCTO #15143]

Signed-off-by: Fabien Mahot <fabien.mahot@smile.fr>
Reviewed-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 9adffbb9)
Signed-off-by: Steve Sakoman <steve@sakoman.com>