Update the documentation at the top of parserTests.txt

The meaning of the php/parsoid options changed slightly with
change Ie4e68960ca7c352af495ebb59ba83488935a44c4.  Update the
documentation comment at the top of the parser test file to match.

Change-Id: If0caac128704a15b824ccbcfbfb3f49812510f1d
Merge "Update the documentation at the top of parserTests.txt"