Apply r41148 again

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41846 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/specification.rb

@@ -2268,7 +2268,7 @@ class Gem::Specification
         require 'rubygems/psych_tree'
       end
 
-      builder = Gem::NoAliasYAMLTree.new({})
+      builder = Gem::NoAliasYAMLTree.create
       builder << self
       ast = builder.tree