Remove specialist topic code from repo

[georges1996]

Ticket: https://trello.com/c/gbfKtIeY/2401-remove-specialist-topic-code-from-search-m

WHAT

Remove some/all references to specialist_sectors from Search API.

WHY

As we are retiring specialist topics.

[hannako]

@kevindew The million dollar question. I don't think so.

• All specialist topics have been archived now https://www.gov.uk/api/search.json?filter_format=specialist_sector
• There was no boosting being applied to documents tagged to specialist topic, boosts are on document type or supergroup
• So if we don't reindex, I think it means that existing documents will still have the specialist-sector field, where as new ones will not (as the mapping has updated). But I don't think there's any negative consequences of that.
• Plus SearchAPI V1 isn't being used for Site Search anymore, so I guess this reduces the risk further.

@leenagupte do you agree?

[leenagupte]

@kevindew The million dollar question. I don't think so.

• All specialist topics have been archived now https://www.gov.uk/api/search.json?filter_format=specialist_sector
• There was no boosting being applied to documents tagged to specialist topic, boosts are on document type or supergroup
• So if we don't reindex, I think it means that existing documents will still have the specialist-sector field, where as new ones will not (as the mapping has updated). But I don't think there's any negative consequences of that.
• Plus SearchAPI V1 isn't being used for Site Search anymore, so I guess this reduces the risk further.

@leenagupte do you agree?

This sounds correct to me. A re-index isn't required for new site search, and it doesn't seem worth the effort to remove a field that isn't being used.