Replace pytest.yield_fixture() with plain pytest.fixture()

yield_fixture is a soft-deprecated alias to fixture now.

Author: bluetech

docs/database.rst

@@ -333,7 +333,7 @@ Put this into ``conftest.py``::
         conn.close()
 
 
-    @pytest.yield_fixture(scope='session')
+    @pytest.fixture(scope='session')
     def django_db_setup():
         from django.conf import settings
 

pytest_django/fixtures.py

@@ -355,7 +355,7 @@ def finalize(self):
         del self._to_restore[:]
 
 
-@pytest.yield_fixture()
+@pytest.fixture()
 def settings():
     """A Django settings object which restores changes after the testrun"""
     skip_if_no_django()