search: remove dead function SearchRepos
Created by: rvantonder
This looks dead as of that other PR that removed a bunch of campaigns stuff. It was introduced as part of https://github.com/sourcegraph/sourcegraph/commit/61c29221e06580e831d6119ab16cfe524928c4f4 and there are no references to type RepoSearcher
or SearchRepos
introduced there.
If we can get rid of this it would help me with a refactor :3