fixup! Fix doc/desc of markers

Author: blueyed

pytest_django/plugin.py

@@ -334,8 +334,7 @@ def get_marker_transaction(test):
         marker = test.get_marker("django_db")
         if marker:
             validate_django_db(marker)
-            if marker:
-                return marker.transaction
+            return marker.transaction
         return None
 
     def has_fixture(test, fixture):