Add missing filter_lot to the Elasticsearch mappings
Add missing filter_lot to the Elasticsearch mappings

"lot" is both a text and a filter field, so it should have both
definitions in the index mapping. Right now, "filter_lot" is created
dynamically by Elasticsearch when the field is first encountered on
document insert.

alphagov/digitalmarketplace-search-api,alphagov/digitalmarketplace-search-api,RichardKnop/digitalmarketplace-search-api,RichardKnop/digitalmarketplace-search-api,RichardKnop/digitalmarketplace-search-api,RichardKnop/digitalmarketplace-search-api