Get rid of some unnecessary commented out code (issue #6849)

There is a lot of false positives (see [attached logs](http://code.google.com/p/sympy/issues/detail?id=3750#c1)), so I don't think that we should automate such cleanup.

fixes #6849
The very first line should have read: "Not sure this one and the one above should be deleted." Sorry for the confusion. That's what I thought I had written.