Merge jelly-require-unicode-7667

Author: wolfgang61
Reviewer: exarkun
Fixes: #7667

Remove the pointless Python-without-unicode support code from
`twisted.spread.jelly`.


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/trunk@43237 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb