Removes double require in spec_helper.

See #1155.

Author: towanda

spec/spec_helper.rb

@@ -12,7 +12,6 @@
 require 'rack/test'
 require 'base64'
 require 'cookiejar'
-require 'json'
 require 'mime/types'
 
 Dir["#{File.dirname(__FILE__)}/support/*.rb"].each do |file|