Fix tests to use rspec expect syntax

spec/spec_helper.rb

@@ -6,7 +6,3 @@ require 'rack/test'
 require 'dyndnsd'
 require 'support/dummy_database'
 require 'support/dummy_updater'
-
-RSpec.configure do |config|
-  config.expect_with(:rspec) { |c| c.syntax = :should }
-end