Remove stems

If we have no custom stemming, then remove it completely else the analyser will explode with an empty list.
Compromise for unified search

Emptied out the registries, this is a gds thing and not needed for ODI.
It blows up if it tries to look for a registry as it'll expect to find one in the
government index, which won't exist. So empty hash it.

I've undone what I had previously for indexes. Tests are quite brittle and
directly tied to the idea of govuk_indexes having multiple items in there,
so don't rename it. While the naming is now a bit wrong and confusing,
by leaving it as govuk_indexes the tests will still run.

Live with it for now.
Skipping migration test for now

This was being tested by changing the stemming rules.

ODI don't have stemming rules, when you do, put this back in.

yes, I know it's a bit "bad" to move a test out the way, but SHIP IT>
Actually name the index we use

*facepalm*