Exclude external RC entries (e.g. Wikidata) from Special:ActiveUsers

People usually want to know who the active users are on the local
wiki, not who edited something on Wikidata.

Note, this changes the query to no longer use a covering index
when joining against the recentchanges table when displaying
the page.

Bug: 63769
Change-Id: I919123f396d0901822108a4675593a2ff5b7307f