In prefix search weight title matches higher

This causes title matches to be weighted higher than redirect matches.  If you
don't do that then you get too many crazy results on enwiki.

Bug: 73636
Change-Id: If4aef14368c89391d623475604dc3077f0d022e2
(cherry picked from commit de7a1dd23da4e8b8242d130422fa3fa0c47a59cb)