Hide the Copy action when the wiki is in readonly mode

Can reproduce this in 16.9.0-SNAPSHOT. As far as I can see on https://github.com/xwiki/xwiki-platform/blob/55d9a5e8c701122f94e0d5808f3e6f322bec6ea5/xwiki-platform-core/xwiki-platform-flamingo/xwiki-platform-flamingo-skin/xwiki-platform-flamingo-skin-resources/src/main/resources/flamingo/menus_content.vm#L23-L30 the pseudo right for the copying action takes from the view right only.

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I'm not sure about the readonly state yet. If it's on one wiki only, it means that we should keep the feature here so that user can keep copying docs from a readonly wiki to another wiki which might not be readonly. If that's a parameter for the whole wiki farm, then there's no point keeping this button here.