Remove setuptools dependency (#346)

* Remove no-longer-necessary test hack
* Remove run-time dependency on setuptools

It was needed for `pkg_resources`-style namespace packages, but that's no
longer a problem here.

Author: cjwatson

CHANGES.rst

@@ -5,7 +5,7 @@
 8.1 (unreleased)
 ================
 
-- Nothing changed yet.
+- Remove run-time dependency on ``setuptools``.
 
 
 8.0 (2025-09-12)

setup.py

@@ -136,7 +136,6 @@ def read(*rnames):
     },
     include_package_data=True,
     zip_safe=False,
-    install_requires=['setuptools'],
     python_requires='>=3.9',
     extras_require={
         'docs': ['Sphinx',

src/zope/interface/common/tests/test_collections.py

@@ -65,10 +65,6 @@ def test_UserString(self):
         # including some that aren't part of a language protocol, such as
         # ``index`` and ``count``.
         memoryview,
-        # 'pkg_resources._vendor.pyparsing.ParseResults' is registered as a
-        # MutableMapping but is missing methods like ``popitem`` and
-        # ``setdefault``.  It's imported due to namespace packages.
-        'ParseResults',
         # sqlite3.Row claims ISequence but also misses ``index`` and
         # ``count``.  It's imported because...? Coverage imports it, but why
         # do we have it without coverage?