[fix bug 1015660] Firefox Privacy Notice update and fix broken links

* Fixed broken links and typo in [bug 1015660](https://bugzilla.mozilla.org/show_bug.cgi?id=1015660).
* Improved link text so things make better sense out of context for screen reader users.
* Also removed the hard-coded `en-US` links for mozilla.org and SUMO, as many of these pages are available in multiple languages (those sites will detect the user language and serve the best one automatically).