Remove unused frontpage:optional

modules/core/locales/ar/LC_MESSAGES/core.po

modules/core/locales/cs/LC_MESSAGES/core.po

modules/core/locales/da/LC_MESSAGES/core.po

modules/core/locales/de/LC_MESSAGES/core.po

modules/core/locales/el/LC_MESSAGES/core.po

modules/core/locales/en/LC_MESSAGES/core.po

modules/core/locales/es/LC_MESSAGES/core.po

modules/core/locales/et/LC_MESSAGES/core.po

modules/core/locales/eu/LC_MESSAGES/core.po

modules/core/locales/fi/LC_MESSAGES/core.po

modules/core/locales/fr/LC_MESSAGES/core.po

modules/core/locales/he/LC_MESSAGES/core.po

modules/core/locales/hr/LC_MESSAGES/core.po

modules/core/locales/hu/LC_MESSAGES/core.po

modules/core/locales/id/LC_MESSAGES/core.po

modules/core/locales/it/LC_MESSAGES/core.po

modules/core/locales/ja/LC_MESSAGES/core.po

modules/core/locales/lb/LC_MESSAGES/core.po

modules/core/locales/lt/LC_MESSAGES/core.po

modules/core/locales/lv/LC_MESSAGES/core.po