Update indonesian nplurals

Summary: We set it to nplurals=1 back then because it was what the KDE translation was using, but after reading the various literature on it, it's pretty clear that indonesian does have a plural form

Reviewers: sdepiets, Localization

Subscribers: kde-i18n-doc, sdepiets

Differential Revision: https://phabricator.kde.org/D19402