Fix shebang in shell_builder (#51)

Summary:
Typo in python shebang introduced by 0d19e27, probably by accident.

Found while skimming the code.
Pull Request resolved: https://github.com/facebook/openr/pull/51

Reviewed By: steven1327

Differential Revision: D21865922

Pulled By: saifhhasan

fbshipit-source-id: 5f2c2c2fac82078070920915812139f5fef1c7fe

build/fbcode_builder/shell_builder.py

-#!/usr/bin/env )python
+#!/usr/bin/env python
 # Copyright (c) Facebook, Inc. and its affiliates.
 from __future__ import absolute_import
 from __future__ import division