Change banned Elasticsearch plugins

The hebrew plugin is a bit unstable - it'll crash some searches.
The unicode plugin should just be better.  Hopefully.  We'll deploy it in
phases by doing in place reindexes in this order:
group0
hebrew wikis

Then we'll wait a few days for soaking, then do group1, soak a few days,
then group2.

Change-Id: I19b5fe468abf4de56b5e446b4606d60b97afb729
Reduce enwiki to 6 Elasticsearch shards

This should make searching faster but will make replication more of a
pain.  We can live with the replication, hopefully.

Change-Id: I12e2881160c38d78191fa40978fc524296a8e3e0
Merge "Change banned Elasticsearch plugins"
Merge "Reduce enwiki to 6 Elasticsearch shards"