RedirectSpecialArticle: Avoid double redirect for action=edit&redlink=1

RedirectSpecialArticle: Avoid double redirect for action=edit&redlink=1

If you visit `Special:MyPage?action=edit&redlink=1` and your user page
exists, this would redirect to `User:Yourname?action=edit&redlink=1`,
which then would redirect further to `User:Yourname`. Just redirect
there directly.

Additionally, the double-redirect seems to somehow conflict with the
fake-redirect code for $wgHideIdentifiableRedirects. I couldn't figure
out why this happens, but you end up on a blank page and no redirect
of either kind occurs.

Bug: T229794
Change-Id: I952fc9df91b1243db22f956ec09bee457c8a21bf