Switch to new Framework :: Zope :: 3 classifier

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

setup.py

@@ -54,7 +54,7 @@ def read(*rnames):
         'Natural Language :: English',
         'Operating System :: OS Independent',
         'Topic :: Internet :: WWW/HTTP',
-        'Framework :: Zope3',
+        'Framework :: Zope :: 3',
     ],
     url='https://github.com/zopefoundation/zope.app.server',
     license='ZPL 2.1',