gyp: remove from __future__ import with_statement

This \_\_future\_\_ import is no longer required in Python >= 2.6.  https://docs.python.org/2/library/__future__.html

PR-URL: #1799
Reviewed-By: Rod Vagg <[email protected]>

Author: cclauss

gyp/pylib/gyp/common.py

@@ -2,8 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-from __future__ import with_statement
-
 import collections
 import errno
 import filecmp