Load stringio with the correct files

Author: hsbt

test/open-uri/test_open-uri.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 require 'test/unit'
 require 'open-uri'
+require 'stringio'
 require_relative 'utils'
 begin
   require 'zlib'

test/open-uri/test_proxy.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 require 'test/unit'
 require 'open-uri'
+require 'stringio'
 require_relative 'utils'
 
 class TestOpenURIProxy < Test::Unit::TestCase

test/open-uri/test_ssl.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 require 'test/unit'
 require 'open-uri'
-require 'stringio'
 require_relative 'utils'
 begin
   require 'openssl'