test_string.rb: defer ENUMERATORS_WANTARRAY to next major

* test/ruby/test_string.rb (TestString::ENUMERATOR_WANTARRAY): defer
  new behavior to next major.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39494 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_string.rb

@@ -6,7 +6,7 @@ def pre_1_7_1
 end
 
 class TestString < Test::Unit::TestCase
-  ENUMERATOR_WANTARRAY = RUBY_VERSION >= "2.1.0"
+  ENUMERATOR_WANTARRAY = RUBY_VERSION >= "3.0.0"
 
   def initialize(*args)
     @cls = String