Documentation: HOWTO: update for 2.6.x -> 3.x versioning in ko_KR

English version HOWTO updated the versioning but Korean version didn't.
Update it now.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>