[URLRewriter] Remove hippotranslation:translated mixin from prototype node

The prototype nodes of the URL Rewriter namespace for all available types (Rule, AdvancedRule, XMLRule) have the mixin hippotranslation:translated.

Is there a reason for this? The impact is a question mark where languages should be shown, see attached picture.

Mind that this is not visible in the urlrewriter demo, because the root folder for the url rewriter perspective is a translated folder. But checking out the project and creating the root folder manually produces a non translated folder, and from that point any urlrewriter documents made in there show the warning in the language menu.