Switch to new Framework :: Zope :: 3 classifier

See zopefoundation/z3c.authviewlet#6 (comment)
for the background behind this.

setup.py

@@ -60,7 +60,7 @@ def alltests():
         'Natural Language :: English',
         'Operating System :: OS Independent',
         'Topic :: Internet :: WWW/HTTP',
-        'Framework :: Zope3'],
+        'Framework :: Zope :: 3'],
     packages=find_packages('src'),
     package_dir={'': 'src'},
     extras_require=dict(