insights: preview search button needs to contain the repos

Created by: Joelkw

The preview search button should include the repos, if you have set repos.

See this example of what currently happens: https://www.loom.com/share/0c59901ba2d14ecebb1bfef86b055471

Expected/better behavior: it should include a repo:github.com/sourcegraph/sourcegraph$ when I preview the search, because I've already told the form that I care about this repo.