fix #1350 Incorrect long months in Japanese

Date resources in Japanese contained an incorrect translation for long months.

Indeed, if you look at the `<months>` tag of this document
http://unicode.org/cldr/trac/browser/tags/release-21-0-2/common/main/jp.xml

and compare it to the same in
http://unicode.org/cldr/trac/browser/tags/release-21-0-2/common/main/en.xml

you can realize that there is no `abbreviated` type. In Japanese, long and short months coincide.