fixes permissions on work package context menu

Fixes: https://www.openproject.org/work_packages/8860
I have to agree that this is confusing and it made me stumble. 
However this is the way it is for now until we clean up the routes. But there is no transitivity here from duplicate to move. Duplicate checks for the ```add_work_packages``` permission and whether the type of the work package copied from is active in the project of the copied work  package. Copy simply uses the ```move_allowed?``` check so it relies on the user to have the ```move_work_packages``` permission.

I am not saying that this makes sense but it mirrors the context menu as it used to be.