Drop data from Elasticsearch we don't need

The big thing this fixes is that having more redirects on a page no longer
makes each redirect worth less.

This also saves about 8.5% of space on my development index.  I'm not sure
how much space it'll save on a more real wiki but it should help.

Bug: 60045
Change-Id: I35528e02e50dac5a89c3022e84c34a99ca800af5
Merge "Drop data from Elasticsearch we don't need"