Revert "ja -> ja-jp"

This reverts commit 422090f140679539cd32e1a9c9d7a42351b144f1.
Revert "ロケールの種類を小文字に統一"

This reverts commit d88a7c352739ae66165a83a5c37b5a775df28866.
Revert "JS側の文言追加とロジック追加"

This reverts commit 6afb35325b13197767d0a26132ec7444aa471e8e.