Remove (accidentally included, I think) Python 3 porting related change.

There is no ClassType on Python 3 but this ticket will just
work on fixing a bug in jelly support of the type type.

refs #4935


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/unjelly-newstyle-reference-cycles-4935@43323 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb