The Retention directories shouldn't be internationalized

To get a uniform structure on Nuxeo vocabularies, we have to remove the French translation field on the RetentionEnd and RetentionEvent vocabularies: there's no reason to add this particular translation when other vocabularies are only translated in English by default.

There's another big concern: you cannot create directory entries with the default Directory.CreateVocabularyEntry automation operation because of the structure of https://github.com/nuxeo/nuxeo-retention/blob/master/nuxeo-retention/src/main/resources/directories/retention_event.csv  => If you set a label, it raises server errors (related to complex properties issues). And if you remove the label, it doesn't work neither. It's a problem when you want to create your custom event in Nuxeo Studio in order to be able to deploy them. It is not to import the vocabulary in the Studio resources and recreate the vocabulary => It breaks Nuxeo when the Studio project is deployed