Revert "[tests] install pytest-responses (#4661)"

This reverts commit ee6b3d8bb6a188d628f50c3593aadf69bd0a1550.

setup.py

@@ -79,7 +79,6 @@ tests_require = [
     # /cassandra
     'datadog',
     'pytest-cov>=1.8.0,<1.9.0',
-    'pytest-responses',
     'pytest-timeout>=0.5.0,<0.6.0',
     'pytest-xdist>=1.11.0,<1.12.0',
     'python-coveralls',

src/sentry/testutils/cases.py

@@ -448,7 +448,6 @@ class CliTestCase(TestCase):
 
 
 @pytest.mark.usefixtures('browser')
-@pytest.mark.withoutresponses
 class AcceptanceTestCase(TransactionTestCase):
     def save_session(self):
         self.session.save()