[SCHEMA] Don't try to do search ranking of contacts.

Summary:
This feature proves to be really expensive during a sync, because you have to
issue many additional database queries to commit a single message. It's also of
dubious utility, when just returning unranked results works pretty all right
for contacts. Many clients will likely also opt to cache all contacts locally
for search-as-you-type level performance.

Test Plan:
Run a sync and check that created objects plus filtered API
responses are correct. I'd like to add more unit tests but don't think that's a
blocker.

Reviewers: spang

Reviewed By: spang

Subscribers: mg

Differential Revision: https://review.inboxapp.com/D306