[web/data] Remove broken backward compatibility function popupLoginBox() was deprecated in favor of cw.htmlhelpers.popupLoginBox() However, the use of cw.utils.deprecatedFunction() is broken. In firebug: >>> popupLoginBox() TypeError: newfunc is undefined cubicweb.js:113 (ligne 13) This function was modified back in 2010, so it's been broken for 4 years. Let's just get rid of it. Closes #4042978