do not show section duplicates when searching via synonyms

> If we assign two synonyms to the same location (heading, commodity) when we search the result appears twice.
> We should dedup the response, so we only show one result, per location.

[pivotal story](https://www.pivotaltracker.com/n/projects/488191/stories/68999382)
remove de-duplication logic

This should be handled by backend. Added in alphagov/trade-tariff-backend#159
Merge pull request #126 from bitzesty/dedup-synonyms

do not show section duplicates when searching via synonyms