I’m not quite sure where the file is used. But since its part of tinymce, it should only be used by some wysiwyg-editor. Since uniweb knows about the issue, maybe there is no need to delete this file anymore.
There should by a file named like “.htaccess.closed.uniweb” (or something like that) in your document root. You have to rename this file to “.htaccess”. Maybe you need to enable the listing of hidden files in your ftp-client.
Uniweb posted on facebook, that they will reopen the websites – so you also could wait a few hours: https://www.facebook.com/UniWeb.no?fref=ts