Merge pb-implementer-7621: use implementer() in twisted.spread

Author: wolfgang61

Reviewer: glyph

Fixes: #7621

Replace the use of zope.interface.implements with zope.interface.implementer in twisted.spread.

git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/trunk@43026 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb