Problem
If you are reading this is because when you are trying to update your Wordpress, it won't update and asks for a SSH username/password instead, as shown in the picture.
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where the first www-data is the user, the second www-data is the group and the path is the root path of Wordpress (the one at bullent bullet point 2)
6 Done. Try to update Wordpress plugins and you should be able to do this now.