Link to mediawiki.org page in 'edithelppage' message

The local page usually does not exist and the link is
of little use to the point it was removed on en.wiki.
The page on mediawiki.org is now translatable with all
old translations imported and ready to get more.

Also mark the message ignored per Siebrand.

Bug: 45977
Change-Id: Ic0469c6c51a4d54ee214347fc416615c2f6cb1f0
Merge "Link to mediawiki.org page in 'edithelppage' message"