Convert BSON::Document to hash before deep_symbolize_keys
Convert BSON::Document to hash before deep_symbolize_keys

Seemingly whichever release of BSON we're now using doesn't work with
deep_symbolize_keys and causes a test to fail, see example below.
This updates the code to convert to a hash first.

Example:
(byebug) item.routes.first.deep_symbolize_keys
{"path"=>"/vat-rates", "type"=>"exact"}
(byebug) item.routes.first
{"path"=>"/vat-rates", "type"=>"exact"}
(byebug) item.routes.first.class
BSON::Document
(byebug) item.routes.first.to_h
{"path"=>"/vat-rates", "type"=>"exact"}
(byebug) item.routes.first.to_h.deep_symbolize_keys
{:path=>"/vat-rates", :type=>"exact"}

alphagov/content-store,alphagov/content-store