changing variable name

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40748 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/psych/lib/psych.rb

@@ -375,10 +375,10 @@ module Psych
   end
 
   ###
-  # Dump Ruby object +o+ to a JSON string.
-  def self.to_json o
+  # Dump Ruby +object+ to a JSON string.
+  def self.to_json object
     visitor = Psych::Visitors::JSONTree.new
-    visitor << o
+    visitor << object
     visitor.tree.yaml
   end