ja: update summary translations (#2474)

Update translations from SUMMARY.md.

Unfortunately, poedit changes the wrapping length of the po files and I
could not get it back by changing the poedit setting for line length. I
believe we won't get any more of these noisy diffs for my further
changes this week.

`Cancellation` is the last item I modified in this PR.

---------

Co-authored-by: Hidenori Kobayashi <[email protected]>

Author: HidenoriKobayashi