Change `retry_if` args in block

[arturictus]

retry_if right now yield the args response, endpoint.

    retry_if do |response, endpoint|
      endpoint.status_code != 200
    end

Will be clearer to pass only the endpoint

    retry_if do |endpoint|
      endpoint.response.class # => Wrappi::Response
    end

[arturictus]

reopen