TranslationDumper consider now <domain>+intl-icu and <domain> as the same domain

[link911]

Actually TranslationDumper::getTranslations() called from DumpCommand consider <domain>+intl-icu and <domain> as two different domains. I think that should not be the case. Context: i have some <domain>.<lang>.xlf mixed to <domain>+intl-icu.<lang>.xlf due to removing transChoice to upgrade symfony version from 3.4 to 4.4 so no more transChoice and welcome intl-icu. Maybe related to issue #312 ? (First PR for me :) )