[FrameworkBundle] Check for 'xlf' instead of 'xliff'
[FrameworkBundle] Check for 'xlf' instead of 'xliff'

There is no translation writer format named 'xliff', but 'xlf' only. So the TranslationUpdateCommand can't be called with 'output-format' == 'xliff' and the version info will never be shown.
symfony/framework-bundle