[Minor] Meld Website Missing Wiki Link on Help Page

[Jesse Sheridan <jesse sheridan gmail com>]

Very minor but the Wiki link is missing at the top on the link bar on
the help page of the main website:
http://meldmerge.org/help/

However, it does show up on the other pages like the homepage:
http://meldmerge.org/

I didn't see the website on github, otherwise I would have submitted a
patch for it.