[tx-robot] updated from transifex

apps/files/l10n/ru.php

apps/files/l10n/sr.php

core/l10n/sr.php

l10n/ar/settings.po

l10n/ar/user_webdavauth.po

l10n/bg_BG/settings.po

l10n/bg_BG/user_webdavauth.po

l10n/ca/settings.po

l10n/ca/user_webdavauth.po

l10n/cs_CZ/settings.po

l10n/cs_CZ/user_webdavauth.po

l10n/da/settings.po

l10n/da/user_webdavauth.po

l10n/de/settings.po

l10n/de/user_webdavauth.po

l10n/de_DE/settings.po

l10n/de_DE/user_webdavauth.po

l10n/el/settings.po

l10n/el/user_webdavauth.po

l10n/eo/settings.po