Remove the downweight_closed_orgs debug parameter

I've been testing this with all the examples we've currently got, and it
downweights the organisations correctly for the example searches, but
still returns them at or near the top for searches for the exact name of
the closed organisation.  Therefore, let's just deploy this without the
parameter.
I don't quite understand the question.  Both boosts need to be applied in queries, though the filters are such that they won't actually both apply to a given document (it would be fine if they did, though).

Or, was it a question about having to define these so precisely in a unit test?  I'd like to refactor the code at some point to make it testable without having to put so many expectations about the shape of unrelated parts of the query into the tests, but that's not a thing to do now.