#1433: put search_repos into SEARCH_METHODS, so the alias is checked against the search quota

[jack5505]

The off-quota guard of Fbe.octo sends a method to the search-quota check only when its name is in Fbe::SEARCH_METHODS. Octokit has search_repos as an alias of search_repositories, and the interceptor sees the name the caller used, so with the search quota at zero search_repositories was stopped while search_repos went to GitHub and got a 403 back.

Added search_repos to Fbe::SEARCH_METHODS; it is the only alias in octokit/client/search.rb. Added a test that calls search_repos with the search quota exhausted and expects Fbe::OffQuota on the search resource; it fails without the fix.

Closes #1433