Switch all English wikis to aggressive splitting

This shouldn't cause too much trouble:  it'll find more results but the
results found through aggressive splitting should be scored lower then
the normal results.  Hopefully that'll be fine.

DEPLOYMENT: Won't do anything at all until the index is rebuilt.

BUG: 63861
Change-Id: I2697c719cd8ee9af106c608ca6477cd404877bb9
Merge "Switch all English wikis to aggressive splitting"