Fix ngettext in DataHelper to make TX happy

core/java/src/net/i2p/data/DataHelper.java

core/locale/messages_ar.po

core/locale/messages_az.po

core/locale/messages_cs.po

core/locale/messages_da.po

core/locale/messages_de.po

core/locale/messages_el.po

core/locale/messages_en.po

core/locale/messages_es.po

core/locale/messages_et.po

core/locale/messages_fa.po

core/locale/messages_fi.po

core/locale/messages_fr.po

core/locale/messages_hu.po

core/locale/messages_in.po

core/locale/messages_it.po

core/locale/messages_ja.po

core/locale/messages_ko.po

core/locale/messages_nb.po

core/locale/messages_nl.po