HOWTO: Change man-page maintainer address for Japanese HOWTO

Below is a patch to change email address of man-page maintainer for
Japanese HOWTO document (Documentation/ja_JP/HOWTO).
This is for sync to Documentation/HOWTO that Michael Kerrisk mentioned
to me.

From: Tsugikazu Shibata <tshibata@ab.jp.nec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>