[SPARK-7933] Remove Patrick's username/pw from merge script

Looks like this was added by accident when pwendell merged a commit back in September: fe2b1d6a

Author: Kay Ousterhout <kayousterhout@gmail.com>

Closes #6485 from kayousterhout/SPARK-7933 and squashes the following commits:

7c6164a [Kay Ousterhout] [SPARK-7933] Remove Patrick's username/pw from merge script