This reverts commit 301b9d88.

#374 overwrote the English version of the solutions

* JA: Fix mistranslation in Horizontal scaling section

- The Japanese translation is ambiguous about “vertical scaling” means scaling out or scaling up.
- The word “expensive” is missing in the Japanese translation.

* ja: Fix mistranslation in "Horizontal scaling"

- Fix mistranslation of parallel structure. (not information/blacklist/limit, but hide/blacklist/limit)

- The Japanese translation is ambiguous about “vertical scaling” means scaling out or scaling up.
- The word “expensive” is missing in the Japanese translation.