docs/ja_JP: translate more of submitting-patches.rst

docs/ja_JP: translate more of submitting-patches.rst

Translate the "Separate your changes", "Style-check your changes",
and "Select the recipients for your patch" sections in
Documentation/translations/ja_JP/process/submitting-patches.rst.

Keep the wording close to the English text and wrap lines to match
the style used in the surrounding Japanese translation.

Signed-off-by: Akiyoshi Kurita <weibu@redadmin.org>
Acked-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260502070143.1015416-1-weibu@redadmin.org>