scm: Ruby 1.9 compatibility for log.

Remove assuming UTF-8 is valid.
"\xC2\x80" of latin-1(iso-8859-1) is valid sequence of UTF-8.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4925 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/changeset.rb

@@ -245,13 +245,6 @@ class Changeset < ActiveRecord::Base
   end
 
   def self.to_utf8(str)
-    if str.respond_to?(:force_encoding)
-      str.force_encoding('UTF-8')
-      return str if str.valid_encoding?
-    else
-      return str if /\A[\r\n\t\x20-\x7e]*\Z/n.match(str) # for us-ascii
-    end
-
     encoding = Setting.commit_logs_encoding.to_s.strip
     unless encoding.blank? || encoding == 'UTF-8'
       begin