Remove python 2.5 compatibility code.

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
+import json
 import logging
 import optparse
 import os
 import re
 import stat
 import sys
 import textwrap
 import urlparse
 import urllib
 import urllib2
 
 try:
   import readline  # pylint: disable=F0401,W0611
 except ImportError:
   pass
 
-try:
-  import simplejson as json  # pylint: disable=F0401
-except ImportError:
-  try:
-    import json  # pylint: disable=F0401
-  except ImportError:
-    # Fall back to the packaged version.
-    sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
-    import simplejson as json  # pylint: disable=F0401
-
 
 from third_party import upload
 import breakpad  # pylint: disable=W0611
 import fix_encoding
 import gclient_utils
 import presubmit_support
 import rietveld
 import scm
 import subprocess2
 import watchlists
@@ skipping 1498 matching lines @@
              'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
 
   # Not a known command. Default to help.
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(main(sys.argv[1:]))