misc: update python scripts to specify python2 or nothing

(Hopefully this changeset will notice my +x to googlecode_upload.py)

Fixes #1217.

R=rsc
CC=golang-dev
https://golang.org/cl/2634041

lib/codereview/codereview.py

-#!/usr/bin/env python
-#
 # Copyright 2007-2009 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

misc/dashboard/googlecode_upload.py

-#!/usr/bin/env python
+#!/usr/bin/env python2
 #
 # Copyright 2006, 2007 Google Inc. All Rights Reserved.
 # Author: danderson@google.com (David Anderson)