List of mentors in Contribute page is unmaintained and outdated

Originally created by @xin on #17076 (Redmine)

Few month ago, when I create tickets about VeraCrypt and Additional software, I didn’t find the information about assignment in this list: https://tails.boum.org/contribute/#mentors

So, who contact about VeraCrypt and Additional software is needed in the Contribute page.

(and in the same time you can remove the reference to Icedove, it was rename long time ago)